Primed marrow for autologous and allogeneic transplantation: A review comparing primed marrow to mobilized blood and steady-state marrow

Experimental Hematology 32 (2004) 327–339

Primed marrow for autologous and allogeneic transplantation: A review comparing primed marrow to mobilized blood and steady-state marrow Gerald J. Elfenbeina and Robert Sacksteinb a

Blood and Marrow Transplant Program, Roger Williams Medical Center, Providence, RI, USA; Departments of Dermatology and Medicine, Brigham and Women’s Hospital, Boston, Mass., USA

b

Mobilized peripheral blood collections, obtained following either chemotherapy (with or without granulocyte colony-stimulating factor (G-CSF)) or G-CSF administration alone, are rapidly replacing traditional bone marrow harvests as the source of cells for hematopoietic stem cell transplantation. According to the Autologous Blood and Marrow Transplant and the International Bone Marrow Transplant Registries, for the years 1998 through 2000, blood stem cell (BSC) transplants accounted for about 80% of autologous transplants in the pediatric age group and more than 90% of the autologous transplants among adults. In allogeneic transplantation, where the donor is a healthy family member or normal volunteer, G-CSF–mobilized BSC transplants are being used more and more frequently, accounting for about 20% of allogeneic transplants in the pediatric age range and more than 40% of allogeneic transplants among adults during the same time period. It is not, therefore, too great a stretch to imagine that BSC transplants will soon be, if not already, in the majority for allogeneic transplantation among adults. The principal reason why this is happening is the prevailing view that BSC engraft more rapidly than marrow stem cells (MSC). However, this view is based on comparisons between primed circulating blood cells (BSC) and unprimed resident marrow cells in the steady state (SS-MSC). If the reason why BSC engraft faster than SS-MSC were a consequence of G-CSF used for mobilization, then would priming of MSC by G-CSF (Prim-MSC) accelerate engraftment of marrow as well? We reviewed the literature of the last 10 years to see if there were enough data to answer this question. 쑖 2004 International Society for Experimental Hematology. Published by Elsevier Inc.

During embryogenesis, hematopoietic stem cells migrate from the yolk sac to the liver and, ultimately, to the medullary cavities of cancellous bones. This migration occurs via the vasculature and, in adult animals, there are persistent but low levels of migrating hematopoietic stem cells in the blood in the steady state. In a canine lethal irradiation model, cross-circulation of blood from an allogeneic dog produced engraftment of donor hematopoiesis as documented by chimerism [1]. In another canine myeloablation model, autologous leukocyte transfusions successfully repopulated marrow spaces and blood elements [2]. These two studies, as well as many others, formally demonstrated the repopulating capacity of circulating hematopoietic stem cells in the bloodstream of large animals.

Offprint requests to: Gerald J. Elfenbein, M.D., F.A.C.P., Adele R. Decof Cancer Center, Roger Williams Medical Center, 825 Chalkstone Avenue, Providence, RI 02908; E-mail: [email protected]

0301-472X/04 $–see front matter. Copyright doi: 1 0. 10 1 6 / j .e x p he m.2 0 04 .0 1 .0 1 0

In man, Goldman [3] reported the first use of blood (albeit Philadelphia chromosome (Ph1)-positive) cells for autologous transplantation after high-dose cytotoxic therapy in patients with chronic myelogenous leukemia (CML). Ko¨rbling et al. [4] reported the first case of Ph1⫺, autologous blood cell transplantation, also in a patient with CML. In a subsequent case report of a patient with Burkitt’s lymphoma, Ko¨rbling et al. [5] introduced the hypothesis that autologous BSC may produce more rapid engraftment than autologous MSC. In both reports by Ko¨rbling, BSC were collected from patients during the overshoot phase of granulocytemacrophage colony-forming units in the blood during leukocyte recovery after cytotoxic chemotherapy. This was the first example of chemotherapy-induced “mobilization,” one of the two major methods we employ today to enrich autologous stem cells in the blood [6]. The modern era of autologous BSC transplantation, however, began with the report by Kessinger et al. [7], which

쑖 2004 International Society for Experimental Hematology. Published by Elsevier Inc.

328

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

documented, with multiple leukaphereses, the presence of sufficient numbers of autologous hematopoietic stem cells in steady-state blood (long after recovery from chemotherapy) to ensure engraftment after myeloablative therapy. Thus, there is little question that adequate hematopoietic progenitors may be obtained from the bloodstream for hematologic recovery after myeloablative treatment. Growth factor–induced mobilization is the second of the two major methods for enriching stem cells in the bloodstream [8]. G-CSF is widely used to mobilize BSC for transplantation. Numerous reports have hypothesized that G-CSF–mobilized BSC (BSC) engraft more rapidly than steady-state MSC (SS-MSC), much as Ko¨rbling had suggested for chemotherapy BSC. Because of the wide acceptance of this hypothesis, G-CSF BSC are being collected more and more often from healthy donors (including unrelated volunteer adult donors) for allogeneic transplantation after myeloablative therapy [9]. Recent reports concerning the induction of proteolysis in the marrow microenvironment by G-CSF have shed light upon what may be the molecular mechanism of growth factor mobilization of progenitor cells [10–13]. G-CSF induces proteolysis of at least CD106 (vascular cell adhesion molecule–1 or VCAM-1), which results, subsequently, in the release of progenitors, capable of repopulating hematopoiesis, into the circulation. What remains unclear at present is why BSC would produce more rapid engraftment than SSMSC. This review may shed light upon this open question.

Literature search The search for articles published over the last 10 years in peer-reviewed, English-language journals and authoritative, English-language monographs comparing BSC and MSC was initiated with PubMed on-line. The search was predicated upon the key words: autologous or allogeneic or HLAidentical; transplantation, stem cell; and blood and/or marrow. Several searches at different times putting the key words in different orders were performed. To be included in our analyses, published articles must have reported comparisons of at least two of the three different types of stem cell products—BSC, SS-MSC, and Prim-MSC. Reference lists from all publications so obtained were also reviewed for additional publications germane to the topic that were not detected via PubMed on-line. Published meeting abstracts were excluded from the analyses performed because of the risk of incomplete data. The search concluded in January 2003. Although meta-analyses are the most sensitive way to detect small differences between study groups, due to the number and heterogeneity of reports examined, it was not feasible to obtain primary data to execute meta-analyses. As an alternative statistical method, which takes into account differences in sample size for different studies, we calculated and report here weighted median stem cell numbers and

weighted median days to engraftment of granulocytes (the first of three days when the absolute granulocyte count (AGC) exceeded 0.5 × 109/L) and platelets (the first of three days when the platelet (PLT) count exceeded 20 × 109/L unsupported by platelet transfusions). Medians were weighted by sample size. In addition, we calculated and report here weighted median T cell numbers and weighted probabilities of five major clinical outcomes: 1) acute graftvs-host disease (GVHD; Grade II or higher), 2) chronic GVHD (extensive and limited), 3) relapse rate (100% minus percentage of patients, at the median follow-up time, remaining relapse free from Kaplan-Meier time to relapse plots), 4) overall survival (percentage of patients, at the median follow-up time, remaining alive from Kaplan-Meier time to death plots), and 5) disease-free survival (percentage of patients, at the median follow-up time, remaining both free of relapse and alive from Kaplan-Meier time to event plots). In this report, we term inter-study comparisons “global” analyses. Also, we term intra-study comparisons “delta” analyses. Intra-study delta analyses minimize the contribution of patient heterogeneity that is introduced by evaluating multiple studies at the same time, to each specific endpoint measurement. The assumption made by delta analyses is that patient heterogeneity for both types of stem cell products in a given study will be very similar. Statistical analyses were performed using Statistica software (Tulsa, OK, USA). Medians for granulocyte and platelet engraftment times were not expected to be normally distributed. Assuming nonparametric distributions of medians, comparisons among stem cell product groups were performed using the Kruskal-Wallis ANOVA and median test. Differences between the medians for engraftment times for two different stem cell products were expected to be normally distributed. The null hypothesis was that the average of deltas was zero. The Z test was used to test the null hypothesis. Delta analyses were performed for the subgroup of studies that were randomized controlled trials first, then, if necessary, for all studies comparing two stem cell products “head-to-head.” To determine risk factors for individual outcomes, we employed an ANCOVA method. All p-values presented are from two-tailed tests.

Results Literature review The objective of the literature search was to assemble as many articles as possible from the modern literature (past 10 years) to evaluate seven clinical outcomes, i.e., engraftment times for granulocytes and platelets, acute and chronic GVHD, relapse rate, overall survival, and disease-free survival. The ultimate goal of the literature review was to determine if there were differences in any of these seven

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

329

clinical outcomes for both autologous and allogeneic transplants based upon anatomic source of stem cells and/or use of G-CSF before collection. As will be seen, the results provide a new perspective to help us formulate a more accurate hypothesis about engraftment relating to the anatomic source of stem cells and the use of G-CSF precollection of BSC (mobilization) and MSC (priming). Thirty-seven articles were collected, 13 reporting autologous transplants [14–26] and 24 reporting allogeneic transplants [27–50]. It was important to identify articles that reported results not only for comparisons of BSC with SSMSC but also for comparisons of Prim-MSC with either BSC or SS-MSC, as well. Autologous transplantation In the autologous stem cell transplant literature, there were 18 eligible comparisons in the 13 reports. There was considerable heterogeneity among the 18 comparisons. There were 9 prospective comparisons (6 with randomization, 2 with assigned controls, and 1 with simultaneous controls) and 9 retrospective comparisons (4 with historical controls, 4 with matched controls, and 1 with sequential patients). Eleven comparisons were from single institutions; 12 comparisons involved lymphoma patients only; 7 comparisons involved a single transplant regimen; and 16 comparisons involved adults only. Eleven comparisons used growth factors during the first 7 days after stem cell infusion (9 with G-CSF and 2 with GM-CSF); growth factors were not administered in 5, and there was no mention of postgrafting growth factors in 2 comparisons. A grand total of 407 patients with BSC were described. Mobilization of BSC was performed in 16 comparisons involving growth factors in 10 (9 with G-CSF and 1 with GMCSF), employing chemotherapy and growth factors in 2, and not described in 4 comparisons. When G-CSF was used to mobilize BSC, the median (range) dose was 10 (5–16) µg/ kg/day for 4 (4–5) days followed by 2 (1–4) leukaphereses. Mobilization of BSC yielded a weighted median (range) of 2.6(1.0–6.4) × 106 CD34⫹ cells/kg. There were 12 comparisons involving SS-MSC describing 347 patients. The weighted median (range) harvest of CD34⫹ cells was 2.1 (1.2–2.3) × 106/kg. There were 9 comparisons involving growth factor Prim-MSC (8 with G-CSF and 1 with GM-CSF) reporting 159 patients. When GCSF was used to prime MSC, the median (range) dose was 10 (1–40) µg/kg/day for 5 (2–5) days followed by a single bone marrow harvest. Priming of MSC yielded a weighted median (range) of 1.5 (0.6–2.3) × 106 CD34⫹ cells/kg. Figure 1 is a graphic presentation of four outcomes of autologous transplants: recovery of granulocytes and platelets, overall survival, and disease-free survival. For the first round of analyses no study was excluded. This round was “global” in nature. As can be seen, there was little difference in the numbers of CD34⫹ cells infused/kg among the three groups—BSC, SS-MSC, and Prim-MSC. The top-to-bottom

Figure 1. For autologous transplants, CD34⫹ cell content of grafts and clinical outcomes. Results for 407 patients who received G-CSF-mobilized blood stem cells (BSC), 347 patients who received steady-state marrow stem cells (SS-MSC), and 159 patients who received G-CSF-primed MSC (Prim-MSC) from 13 different studies (see refs. [14–26]) are shown. Twotailed values of p are given.

spread was 2.6 to 1.5 × 106 CD34⫹ cells/kg, representing a spread of less than a factor of 2. Both AGC and PLT recoveries were, however, delayed for SS-MSC and PrimMSC as compared to BSC. Prim-MSC recoveries were more rapid than SS-MSC, demonstrating a salutary effect of growth factor priming on MSC despite the fact that PrimMSC contained about 25% fewer CD34⫹ cells (per kilogram recipient body weight) than did SS-MSC. Interesting is the observation that Prim-MSC engraft nearly as rapidly as BSC despite having 40% fewer CD34⫹ cells than BSC. Overall survival at a median follow-up of 3.6 years was essentially identical for BSC and SS-MSC. Disease-free survival at a median follow-up of 2.8 years was similar for all three classes of stem cells with a potential edge for MSC. Altogether this global analysis would speak to faster engraftment for BSC, which would translate into briefer aplasias, reduced infections, and fewer transfusions resulting in lower costs, but without an ultimate long-term survival benefit [51–52]. However, because of the extraordinary degree of heterogeneity among the comparisons, as described above, we felt that the global analysis was, by itself, insufficient to draw conclusions. The second round of analyses (“delta” analyses) evaluated only prospective randomized controlled trials (RCT). In this round, analysis of engraftment involved calculating the delta (signed days of difference in the medians) in engraftment times between the two arms of the RCT. There were 4 RCT [14,16,18,26] that compared BSC and SS-MSC and 2 RCT [19,24] that compared BSC to PrimMSC. There were no RCT comparing SS-MSC or Prim-MSC. When delta is positive, it signifies faster recovery for BSC relative to its comparator (SS-MSC or Prim-MSC); when delta is negative, the reverse is true. Although a delta

330

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

of ⫹1 day for AGC recovery may be mathematically significant due to the tightness of distribution of engraftment times [53], such a delta is not clinically meaningful because it signifies, usually, only one more day of antibiotics. Similarly, a delta of ⫹2 days for PLT recovery may be mathematically significant but not clinically meaningful because it represents, ordinarily, only one more platelet transfusion. Figure 2A shows that BSC produced more rapid granulocyte engraftment than SS-MSC in 3 of 4 RCT. Further, in 2 of 2 RCT, BSC and Prim-MSC produced equivalent engraftment times. Figure 2B shows that BSC produced more rapid platelet engraftment than SS-MSC in 3 of 4 RCT. Further, in 2 of 2 RCT, BSC and Prim-MSC produced equivalent engraftment times. In contrast to the global analysis above, this RCT analysis points to equivalence of engraftment potential for both autologous MSC and BSC collected after G-CSF treatment. Furthermore, with respect to overall and disease-free survival, 5 RCT were evaluable. Four of 5 RCT showed equivalence of overall survival while 1 of 5 showed an advantage for BSC [14]. All 5 RCT showed equivalence of disease-free survival for MSC and BSC. Allogeneic transplantation In the allogeneic stem cell transplant literature, 24 manuscripts report eligible comparisons. There was considerable heterogeneity among the 24 comparisons. There were 10 randomized prospective studies, 5 studies with historical controls, 4 retrospective registry studies, 2 studies with case controls, 2 sequential studies, and 1 allocated study. Fifteen comparisons were from single institutions; only 2 comparisons involved only one diagnosis (but not the same one); only 7 comparisons involved a single transplant regimen;

Figure 2. For autologous transplants, delta analysis of engraftment times from randomized controlled trials. Panel A shows the number of days for granulocyte recovery (to ⬎0.5 × 109/L) that G-CSF-mobilized blood stem cells (BSC) engraft faster than steady-state marrow stem cells (SS-MSC) and G-CSF-primed MSC (Prim-MSC). Biologically significant differences are indicated by days more than what the arrow marks (in this case, more than one day). Panel B shows the number of days for platelet recovery (to ⬎20 × 109/L) that BSC engraft faster than SS-MSC and Prim-MSC. Biologically significant differences are indicated by days more than what the arrow marks (in this case, more than two days).

but 22 comparisons involved adults only. Acute GVHD prophylaxis involved cyclosporine in 22 studies (with 2 making no mention). In addition, methotrexate was given to all patients in 15, some patients in 6, and no patients in 2 studies, but was not mentioned in 1 study. G-CSF use during the first 7 days after stem cell infusion was routine in 7, sometimes in 4, not routine in 4, not allowed in 4, but not mentioned in 5 studies. A grand total of 1949 patients with BSC were described. Mobilization of BSC was performed in 22 comparisons; methodology involved G-CSF in 19 but was not reported in 3 comparisons. To mobilize BSC with G-CSF, the median (range) dose was 10 (5–16) µg/kg/day for 4 (3–5) days followed by 2 (1–4) leukaphereses. Mobilization specifics (dose, schedule, duration, and number of collections) were not completely described in 4 comparisons. Mobilization of BSC with G-CSF yielded a weighted median (range) of 6.1 (3.1–12.3) × 106 CD34⫹ cells/kg. There were 21 comparisons involving SS-MSC describing 3782 patients. The weighted median (range) harvest of CD34⫹ cells was 3.2 (1.5–7.5) × 106/kg for SS-MSC. There were only 5 comparisons involving G-CSF Prim-MSC reporting 107 patients. To prime MSC with G-CSF, the median (range) dose was 10 (4–10) µg/kg/day for 4 (2–7) days followed by a single bone marrow harvest. Priming of MSC yielded a weighted median (range) of 4.1 (1.6– 9.4) × 106 CD34⫹ cells/kg. The regimens involving G-CSF treatment prior to collecting BSC and Prim-MSC were virtually identical. Figure 3 is a graphic presentation of 7 outcomes of allogeneic transplants: recovery of granulocytes and platelets, acute and chronic GVHD, relapse rate, overall survival, and disease-free survival. The medians for recovery of granulocytes and platelets for each stem cell product for all studies

Figure 3. For allogeneic transplants, CD34⫹ and CD3⫹ cell content of grafts and clinical outcomes. Results for 1949 patients who received G-CSF-mobilized blood stem cells (BSC), 3782 patients who received steady-state marrow stem cells (SS-MSC), and 107 patients who received GCSF-primed MSC (Prim-MSC) from 24 different studies (see refs. [27– 50]) are shown. Two-tailed values of p are given.

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

are tabulated in Tables 1 and 2. For the “global” round of analyses no study was excluded. As can be seen, there was little difference in the numbers of CD34⫹ cells infused/ kg among the three groups—BSC, SS-MSC, and Prim-MSC. The top-to-bottom spread was 6.2 to 3.2 × 106 CD34⫹ cells/ kg, representing a spread of slightly less than a factor of 2. Both AGC and PLT recoveries were delayed for SS-MSC compared to BSC. As seen in autologous transplants, PrimMSC recoveries after allogeneic transplants were much more rapid than SS-MSC, also demonstrating a beneficial effect of G-CSF priming on MSC. Interestingly, Prim-MSC contained only about 30% more CD34⫹ cells than SS-MSC. Most remarkably, AGC and PLT recoveries were identical for Prim-MSC and BSC even though Prim-MSC contained about 30% fewer CD34⫹ cells than BSC. One significant difference among stem cell products is that BSC contain nearly sevenfold more CD3⫹ cells/kg than SS-MSC or Prim-MSC. No significant differences for acute

331

GVHD were reported among SS-MSC, BSC, and PrimMSC. However, SS-MSC produced less chronic GVHD than BSC and Prim-MSC produced even less chronic GVHD than SS-MSC. Despite the differences in the incidence of chronic GVHD, the probability of relapse at a median followup of 2.4 years was certainly not higher for SS-MSC or PrimMSC than for BSC. Overall survival at a median follow-up of 1.9 years was essentially identical for BSC, SS-MSC, and Prim-MSC. Finally, disease-free survival at a median follow-up of 1.9 years was similar for BSC and SS-MSC. (There were insufficient disease-free survival data to report for Prim-MSC.) Altogether the global analysis would speak to equivalent engraftment potential for both G-CSF BSC and G-CSF PrimMSC, both of which are superior to SS-MSC. Even though the numbers of patients receiving Prim-MSC are limited (n ⫽ 107), it is safe to say that there is no more acute GVHD with Prim-MSC and perhaps less chronic GVHD than with

Table 1. Delta analysis of allogeneic trials for granulocyte recovery Median Day to AGC ⬎ 0.5 × 109/L Comparison/ Author (ref no.) BSC vs SS-MSC Korbling [33] Schmitz [38] Bensinger [35] Hassan [34] Szer [41] Vigorito [39] Mahmoud [40] Nagatoshi [48] Guardiola [47] Couban [28] Faucher [37] Champlin [43] Nivison-Smith [46] Ringden [29] Bensinger [27] Pavletic [36] Powles [44] Blaise [42] Heldal [45] BSC vs SS-MSC Prim-MSC vs SS-MSC Ji [49] Isola [30] Prim-MSC vs SS-MSC BSC vs Prim-MSC Serody [31] Elfenbein [50] Morton [32] BSC vs Prim-MSC

Design of Controls

No. of Patients In 1st vs 2nd Columns at Right

BSC

SS-MSC

Prim-MSC

Delta of Medians for AGC

historical randomized case control historical randomized randomized randomized historical registry randomized case control registry registry registry randomized historical randomized randomized randomized overall

16 vs 25 33 vs 33 81 vs 91 31 vs 26 13 vs 14 18 vs 19 15 vs 15 16 vs 24 102 vs 132 109 vs 118 17 vs 17 288 vs 536 44 vs 79 946 vs 2363 37 vs 37 21 vs 22 20 vs 19 48 vs 52 28 vs 30 averages

9 14 14 15 17 16 9 11 14 19 14 14 14 14 16 11 17.5 15 17 14.2

9 15 16 17 19 18 13 15 18 23 19 19 19 19 21 16.5 23 21 23 18.1

-

0 1 2 2 2 2 4 4 4 4 5 5 5 5 5 5.5 5.5 6 6 3.84∗

allocated historical overall

18 vs 32 112 vs 10 averages

-

21 26 23.5

15 14 14.5

6 12 9.0†

sequential sequential randomized overall

20 vs 26 17 vs 11 29 vs 28 averages

17 12 14 14.3

-

16 11 14 13.7

-1 -1 0 -0.67‡

∗Difference in days to AGC ⬎ 0.5 × 109/L for SS-MSC minus BSC, p ⬍ 0.001. BSC faster than SS-MSC. † Difference in days to AGC ⬎ 0.5 × 109/L for SS-MSC minus Prim-MSC. Prim-MSC faster than SS-MSC. Sample size too low to do statistical comparison to zero but range does not include zero. ‡ Difference in days to AGC ⬎ 0.5 × 109/L for Prim-MSC minus BSC, p ⬍ 0.20. Prim-MSC equivalent to BSC. Abbreviations: AGC ⫽ absolute granulocyte count; BSC ⫽ G-CSF-mobilized blood stem cells; SS-MSC ⫽ steady-state marrow stem cells; PrimMSC ⫽ G-CSF-primed marrow stem cells.

332

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

Table 2. Delta analysis of allogeneic trials for platelet recovery Median Day to PLT ⬎ 20 × 109/L Comparison

Author (ref no.)

Controls

BSC

SS-MSC

Prim-MSC

Delta of Medians for PLT

Schmitz [38] Bensinger [35] Hassan [34] Vigorito [39] Couban [28] Bensinger [27] Korbling [33] Champlin [43] Szer [41] Mahmoud [40] Blaise [42] Heldal [45] Powles [44] Faucher [37] Pavletic [36] Nivison-Smith [46] Ringden [29] Guardiola [47] Nagatoshi [48] overall

randomized∗ case control historical randomized randomized randomized historical registry randomized randomized randomized randomized randomized case control historical registry registry registry historical averages

15 11 15 12 16 13 12 18 17 10 13 13 11 15 13 17 16.7 16 12 14.0

19 15 20 17 22 19 19 25 25 18 21 21 20.5 25 24 28 28 28 26 22.1

-

4 4 5 5 6 6 7 7 8 8 8 8 9.5 10 11 11 11.3 12 14 8.15†

Isola [30] Ji [49] overall

historical allocated averages

-

26 24 25.0

20 17.5 18.8

6 6.5 6.25‡

Elfenbein [50] Morton [32] Serody [31] overall

sequential randomized sequential averages

19 12 13 14.7

-

17 14 16 15.7

BSC vs SS-MSC

BSC vs SS-MSC Prim-MSC vs SS-MSC

Prim-MSC vs SS-MSC BSC vs Prim-MSC

BSC vs Prim-MSC

-2 2 3 1.0||

∗For number of patients in each arm, see Table 1. † Difference in days to PLT ⬎ 20 × 109/L for SS-MSC minus BSC, p ⬍ 0.001. BSC faster than SS-MSC. ‡ Difference in days to PLT ⬎ 20 × 109/L for SS-MSC minus Prim-MSC. Prim-MSC faster than SS-MSC. Sample size too low to do statistical comparison to zero but range does not include zero. || Difference in days to PLT ⬎ 20 × 109/L for Prim-MSC minus BSC, p ⬍ 0.60. Prim-MSC equivalent to BSC. Abbreviations: PLT ⫽ platelet count; BSC ⫽ G-CSF-mobilized blood stem cells; SS-MSC ⫽ steady-state marrow stem cells; Prim-MSC ⫽ G-CSFprimed marrow stem cells.

BSC. Further, as relapse, survival, and disease-free survival are likely to reflect disease state (remission or relapse number) and transplant regimen as well as the salutary effect of GVHD, it is safe to say that Prim-MSC are likely to produce outcomes as good as BSC. From the global analysis, the only clinically meaningful difference detected between MSC and BSC collected after G-CSF treatment is the reduction of the incidence of chronic GVHD [54]. Again, because of the extraordinary degree of heterogeneity among the comparisons, as described above, a round of delta analyses was performed. In this second round, only prospective RCT were evaluated. Again, this RCT analysis involved the delta in engraftment times (as described above) between the two arms of the studies. There were 9 RCT [27,28,38–42,44,45] that compared BSC and SS-MSC but only 1 RCT [32] that compared BSC to Prim-MSC. There were no RCT comparing SS-MSC to Prim-MSC. By the same criteria (delta ⬎ 1 for granulocytes and delta ⬎ 2 for

platelets) as described above, BSC produced more rapid granulocyte engraftment than SS-MSC in 8 of 9 RCT. In the sole RCT of its kind, BSC and Prim-MSC produced equivalent granulocyte engraftment times. BSC produced more rapid platelet engraftment than SS-MSC in 9 of 9 RCT. But in the single RCT, BSC and Prim-MSC produced equivalent platelet engraftment times [32]. Because there was only one RCT comparing BSC to Prim-MSC, it was deemed necessary to perform at least one more analysis. The third round of analyses extended delta analyses to all comparisons. Utilizing deltas in engraftment times, studies were arranged by type of comparison and sorted by delta in ascending order. The results for granulocyte engraftment are presented in Table 1 and for platelet recovery in Table 2. As can be seen for granulocytes, 17 of 19 comparisons have a delta greater than 1 for BSC compared to SS-MSC. Also, 2 of 2 comparisons of Prim-MSC vs SS-MSC have delta

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

greater than 1. Finally, 0 of 3 comparisons of BSC vs PrimBSC have a delta greater than 0, let alone delta greater than 1. As can be seen for platelets, all 19 comparisons have a delta greater than 2 for BSC compared to SS-MSC. Also, 2 of 2 comparisons of Prim-MSC vs SS-MSC have a delta greater than 2. Finally, only 1 of 3 comparisons of BSC vs Prim-BSC has a delta greater than 2 (and that delta is 3). Taking all of these three analyses together, it appears that allogeneic G-CSF Prim-MSC have the same engraftment potential as G-CSF-mobilized BSC. We believe that the functional capacity of Prim-MSC is the best measure of the repopulation potential of the marrow left behind after mobilization of BSC with G-CSF. Therefore, it appears that there should be only minimal concern about donor long-term hematopoiesis. Next, chronic GVHD was less frequent with SS-MSC and Prim-MSC than with BSC but overall and disease-free survival were the same. Although chronic GVHD has a well documented graft-vs-leukemia/lymphoma effect, the reduction of chronic GVHD seen with SS-MSC and Prim-MSC was not associated with an increase in relapse rates. Factors influencing pace of engraftment The literature review enabled us to collect data on a variety of clinical factors (from both autologous and allogeneic transplants) that may influence the pace of engraftment of granulocytes and platelets. Factors potentially relevant to the pace of engraftment included anatomic source of stem cells, use of G-CSF pretreatment prior to collecting stem cells from either source, dose of CD34⫹ cells/kg delivered to patient, use of G-CSF during the first 7 days after transplant, use of methotrexate as part of prophylaxis to prevent acute GVHD, diagnosis, and high-dose chemotherapy regimen. When median times to granulocyte and platelet recovery were plotted on a histogram, we noted that there was a normal distribution (as opposed to our nonparametric assumptions). This permitted us to use ANCOVA methodology to attempt to determine which of these factors, if any, may have had a significant influence upon the median day to recovery of granulocytes and platelets. For autologous transplantation, the dose of CD34⫹ cells/ kg is well known to be associated with time to engraftment for BSC [55]. The simplest fit mathematical equation describing this relationship is a hyperbolic function in which day of engraftment ⫽ constant ⫹ 1/(function of cell dose) [56]. Therefore, it was no surprise that, when a univariate analysis of median day to engraftment with CD34⫹ cell dose was performed, CD34⫹ cell dose was significantly related to the time of engraftment. However, quite surprisingly, when the use of G-CSF prior to collecting stem cells was entered into a bivariate analysis, CD34⫹ cell dose was no longer significantly associated with pace of engraftment. When additional variables were added to perform a full multivariate analysis, CD34⫹ cell dose was again

333

not associated with time to engraftment (see Table 3). Reexamination of Figure 1 gives a graphic overview of this analysis because patients receiving Prim-MSC recovered granulocyte and platelet counts more rapidly than those receiving SS-MSC despite receiving one quarter fewer CD34⫹ cells (weighted median 1.5 × 106/kg vs 2.1 × 106/kg). The only factor that had a significant impact on engraftment was the use of G-CSF prior to collecting stem cells from either blood or marrow. For allogeneic transplantation, the results of the multivariate analyses were very interesting as well. As shown in Table 3, for granulocyte recovery, CD34⫹ cell dose, the use of G-CSF during the first 7 days after engraftment, the use of methotrexate as part of prophylaxis for acute GVHD, and the stem cell product were all variables significantly and independently associated with pace of engraftment. CD34⫹ cell dose was important for granulocyte but not platelet recovery. The value of using G-CSF after engraftment has long been known for SS-MSC [57] but has been a subject for debate with BSC. Our analysis pointed to a significant and independent role for G-CSF for granulocyte but not platelet recovery (as might be expected). Because use of methotrexate has long been known to delay allogeneic engraftment [55], it came as no surprise that methotrexate negatively but significantly influenced time to engraftment of granulocytes but, quite to our surprise, methotrexate had no impact upon engraftment of platelets. The interaction term told us that G-CSF pretreatment and not anatomic source was responsible for accelerating engraftment by BSC and PrimMSC of both granulocytes and platelets. Reexamining Figure 3, we see that Prim-MSC produced as rapid engraftment as BSC but with roughly one-third lower dose of CD34⫹ cells (4.1 × 106/kg vs 6.1 × 106/kg) and Prim-MSC engraft much faster than SS-MSC with but one-third more CD34⫹ cells (4.1 × 106/kg vs 3.2 × 106/kg). Identifying factors that may influence the kinetics of engraftment must be interpreted with a degree of caution because the studies were not designed to answer this question, nor is the analysis a true meta-analysis. However, these findings are provocative and may provide rationale and incentive for future prospective RCT.

Discussion In the years 2001 and 2002, six publications appeared in peer-reviewed journals comparing engraftment kinetics of stem cells derived from peripheral blood and bone marrow in allogeneic transplants [27–29,46–48]. In these six publications, blood stem cells were observed to produce more rapid recovery of granulocytes and platelets than marrow stem cells. In all six reports, BSC were mobilized by G-CSF but MSC were collected in the steady state. These data supported the hypothesis that BSC engraft more rapidly than MSC, a hypothesis that was based upon at least 13 publications in the allogeneic literature through the year 2000 [33–45].

334

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

Table 3. Multivariate analyses for clinical factors influencing pace of engraftment Two-tailed p for Median Days to Clinical Factor Autologous transplants CD34⫹ Cell Dose ( × 106)/kg

Favorable Variable AGC ⬎ 500 × 109/L PLT ⬎ 20 × 109/L more

0.800

0.110

Use of G-CSF during First 7 Days Posttransplant Characteristics of Stem Cell Product 1. Anatomic Source of Stem Cells

yes

0.660

0.273

BSC

0.012

0.053

2. Precollection Use of G-CSF

not SS-MSC

0.031

0.071

Allogeneic Transplants CD34⫹Cell Dose ( × 106)/kg

more

0.013

0.965

Use of G-CSF during First 7 Days Posttransplant Use of Methotrexate as Part of Acute GVHD Prevention Characteristics of Stem Cell Product 1. Anatomic Source of Stem Cells

yes

0.002

0.711

no

0.001

0.984

BSC

0.395

0.023

2. Precollection Use of G-CSF

not SS-MSC

0.050

0.008

However, there are now five reports in the literature [30– 32,49,50] evaluating the engraftment kinetics for Prim-MSC. In two of these five reports, G-CSF Prim-MSC have been shown to engraft more rapidly than SS-MSC. In three of these five reports, G-CSF Prim-MSC engrafted as rapidly as did G-CSF BSC. These five reports suggest that the hypothesis that BSC engraft more rapidly than MSC needs reexamination if not reformulation. Several reports have appeared in the literature in 2001 and 2002 demonstrating that G-CSF induces neutrophil proteases in the marrow microenvironment that cleave VCAM1 (CD106), an event that appears to be mechanistically related to the release of hematopoietic progenitors into the circulation. Clinically, this is termed “mobilization” [10– 13]. It has also been shown that chemotherapy induces the same proteolytic environment [11]. The proteolytic environment may produce damage to stem cells remaining resident in the marrow or damage to the marrow stroma after routine use of chemotherapy (with or without G-CSF). The consequences of the proteolytic environment are not a critical factor in patients with malignancies, as chemotherapy is necessary to treat their malignancies. However, this proteolytic environment may possibly be one of the explanations why up to 20% of eligible autologous transplant patients cannot have sufficient numbers (qualitatively as well as quantitatively) of stem cells mobilized into the bloodstream to ensure rapid engraftment after high-dose therapy. More importantly, the potential that this proteolytic environment may produce permanent stem cell damage in healthy donors is an issue that needed to be addressed, especially now that

Comment Autologous engraftment is independent of CD34⫹ cell dose. G-CSF after autologous transplant does not accelerate engraftment. BSC engraft faster than MSC only when Prim-MSC & SS-MSC are combined. SS-MSC engraft slower than G-CSF–pretreated stem cells (BSC & Prim-BSC combined). Allogeneic engraftment is dependent on CD34⫹ cell dose but only for AGC. G-CSF after transplant accelerates engraftment but only for AGC. Methotrexate delays engraftment but only for AGC. Only for PLT do BSC engraft faster than MSC & only when Prim-MSC & SS-MSC are combined. SS-MSC engraft slower than G-CSF–pretreated stem cells (BSC & Prim-MSC combined).

unrelated volunteer donors are being mobilized with G-CSF to collect BSC [9]. Gratifyingly, this review shows that this proteolysis does not appear to damage the marrow in a manner that would be detrimental to a healthy donor (e.g., damage to the microenvironment or depletion of stem cells) because Prim-MSC, the very MSC remaining after G-CSF treatment to mobilize and collect BSC, retain their early engraftment potential. The effects of this proteolysis upon the marrow microenvironment remain to be determined. The literature review examining the engraftment of GCSF Prim-MSC allows us to achieve a better understanding of the results of early studies about BSC and MSC that, today, seem to be in contradistinction to the prevailing hypothesis that BSC engraft more rapidly than MSC. First, granulocyte recovery after autologous stem cell transplantation was very slow when steady-state BSC (SS-BSC) were employed (median day 22 (11–58)) [7] as compared to when autologous chemotherapy and G-CSF-mobilized BSC were employed (median day 10 (8–52)) [55]. Second, autologous SS-BSC produced apparently slower granulocyte recovery [7] than did allogeneic SS-MSC (median day 14 (10–37)) when methotrexate was not used along with cyclosporine for acute GVHD prophylaxis [55]. And third, in an RCT, there was no acceleration of granulocyte engraftment when autologous SS-BSC were added to autologous SS-MSC as compared to autologous SS-MSC alone (medians 27 vs 20 days) for granulocyte recovery [58]. Data concerning platelet recovery show the same relationships: autologous SS-BSC, median day 23 (14–56); autologous chemotherapy and GCSF BSC, median day 17 (8–75); and allogeneic SS-MSC,

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

median day 25 (11–81). Finally, for platelet recovery, autologous SS-BSC combined with autologous SS-MSC did not engraft more rapidly than autologous SS-MSC alone (medians 27 vs 22 days) [58]. Altogether these data suggest that, in terms of engraftment, steady-state BSC have no better engraftment potential than steady-state MSC. If, as described above, SS-BSC and SS-MSC have equivalent engraftment potential and if, as summarized by this review, Prim-MSC and mobilized BSC have equivalent engraftment potential, then we must develop a new hypothesis about engraftment; to wit, MSC and BSC have equivalent engraftment potential and G-CSF enhances the engraftment potential of both MSC and BSC equally as well. This G-CSF-induced acceleration of engraftment is seen when G-CSF pretreatment is identical before leukapheresis for BSC and before marrow harvest for Prim-MSC. Autologous transplantation is not the best model system for verifying the validity of this new hypothesis because of the tremendous heterogeneity introduced in the engraftment potential of collected stem cells due to prior chemotherapy and the effects of different transplant preparative regimens upon engraftment [55,57,59,60]. Indeed, at least one group of investigators did not find that G-CSF priming accelerated engraftment of MSC at all [17]. However, this one negative observation cannot outweigh the several positive observations [61]. More importantly, we have previously reported acceleration of engraftment by G-CSF priming of autologous MSC [62] and carried this observation through an RCT, which demonstrated equivalent engraftment for both BSC and Prim-MSC [24]. The argument could be proffered that there are an insufficient number of autologous RCT to support the new hypothesis. The principles of evidencebased medicine hold that RCT (phase III trials) are considered the gold standard in clinical research. However, there are new data that reveal non-RCT (phase II trials) establish biological principles with the same durability of validity as do RCT [63]. This provides us with an entirely new perspective for examining the published literature. Allogeneic transplantation is a far better human model because health of donor marrow is not in question as it is in patients with malignancies. In comparative studies, many more allogeneic transplants involving BSC (n ⫽ 1949), SSMSC (n ⫽ 3782), and G-CSF Prim-MSC (n ⫽ 107) have been reported than autologous transplants involving the same three groups (BSC, 407; SS-MSC, 347; and PrimMSC, 159). The numbers of Prim-MSC transplants are few but the data are clear. In the global analysis, in the examination of RCT only, and in delta analysis comparisons of all studies, the allogeneic data support the new hypothesis that stem cell engraftment potential is not predetermined by the anatomic site of collection but rather by the effects of GCSF upon the collected cells. The new hypothesis we postulate may be confirmed by RCTs in which the following parameters are held constant for all patients in the study: only one age group, a single

335

diagnosis and state of disease (preferably first complete remission for the acute myelogenous leukemia to minimize induction chemotherapy variability), a limited interval between demonstration of remission and transplant, a fixed G-CSF pretreatment regimen, standardized collection of stem cells by leukaphereses and by bone marrow harvest, one transplant preparative regimen, infusion of a specified and equal number of CD34⫹ cells for both BSC and MSC, a single anti-GVHD immunosuppressive regimen (preferably without methotrexate), and one policy concerning use of GCSF postgrafting. This is a tall order and, to be accomplished, would likely require a large number of institutions and probably international collaboration. The number of institutions required adds additional variability, but the variability may be manageable by stratification by institution. The likelihood that this will be done in the near future is poor. In the meantime, clinicians need to decide care for their patients with the data at hand. This brings up other observations about outcomes that can be addressed. Contamination of stem cell collection could be a determinant in choosing the anatomic source of stem cells (BSC vs MSC) for autologous transplantation. But this does not appear to be a major consideration, at least for lymphomas [64]. Healthy donor anxiety and donor choice could be a factor in determining the source of stem cells were there not other important clinical considerations for the patient receiving allogeneic transplantation (vide infra) [65]. For autologous transplantation, relapse rate, overall survival, and disease-free survival are very important clinical outcomes. A recent publication concerning patients with non-Hodgkin’s lymphoma (NHL) only, transplanted after a single preparative regimen, showed an overall survival benefit for BSC over SS-MSC but no disease-free survival advantage [14]. Four other RCT, involving germ cell cancer (1), NHL and Hodgkin’s disease combined (2), and breast cancer (1), treated by four different high-dose regimens show no disease-free survival advantage for BSC over SS-MSC [16,23,24,26]. Moreover, none of these four RCT shows an overall survival advantage for BSC over SS-MSC. The sentinel article [14] is a perfect demonstration that overall survival is not the best measure of value of a therapy, especially if there are good salvage therapies to prolong life after relapse [53]. As limited as the global analysis may be, there does not appear to be a consistent advantage of BSC over SS-MSC insofar as survival and disease-free survival are concerned. This is all the more meaningful when considering that the median follow-up after autologous transplantation for overall survival was 3.6 years and 2.8 years for diseasefree survival. In allogeneic transplantation, acute and chronic GVHD, in addition to relapse rate, overall survival, and disease-free survival, are very important clinical outcomes. No comparative engraftment study reported so far had primary endpoints of either GVHD, relapse, or survival. Evaluations of secondary endpoints have resulted in reports showing advantage

336

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

for SS-MSC over BSC in terms of reduced incidence of chronic GVHD [27,32,54,66]. Our global analysis supports this observation. The mechanism for this effect may be the nearly one log fewer CD3⫹ cells/kg in SS-MSC compared to BSC and/or vastly fewer regulatory NK-T cells and/or CD4⫹/CD25⫹ regulatory T cells in BSC compared to SSMSC, leading to reduction in GVHD potential of marrow T cells [67,68]. Furthermore, pretreatment of the donor with G-CSF may also reduce the potential of Prim-MSC to produce GVHD vis a´ vis SS-MSC [69]. With respect to relapse and survival outcomes, two large RCT suggested that overall survival was improved for recipients of BSC compared to SS-MSC [27,28]. However, looking at all nine of the prospective allogeneic RCT since 1998, there are four (including the two above) that show better overall or diseasefree survival results for BSC and five that show equivalence of SS-MSC (n ⫽ 2) or better results for SS-MSC (n ⫽ 2) or Prim-MSC (n ⫽ 1). Moreover, a multicenter RCT comparing CD34⫹ cells selected from BSC and SS-MSC demonstrated improved survival for patients with hematologic malignancies and myelodysplasia receiving CD34⫹ cells selected from SS-MSC [70]. Our global analysis reflects this variability in observations by showing no particular overall or disease-free survival for BSC over SS-MSC. On the one hand, although Prim-MSC appear to have at least equivalent if not better outcomes when compared to BSC, there are too few Prim-MSC patients to draw definitive conclusions at this time. On the other hand, taking all of the observations about GVHD, relapse, and survival together, it would appear that selecting Prim-MSC as the stem cell product may be appropriate because of less chronic GVHD. Less chronic GVHD could mean less graft-vs-malignancy effect, which may translate into poorer overall survival [27,28]. Resolving these issues is why carefully performed studies are required to determine the balance. Increasing the number of patients in the trial we proposed above would improve the power to detect differences in GVHD incidence, relapse rates, and survival outcomes as well. G-CSF does mobilize stem cells from the marrow, most likely via proteolysis [10–13], but both BSC and the residual MSC (i.e., Prim-MSC) have the same engraftment potential. It appears that BSC collected in the steady state have the same engraftment potential as SS-MSC. Finally, SS-BSC and SS-MSC engraft more slowly than Prim-MSC and BSC. This difference in engraftment kinetics cannot be explained by differences in CD34⫹ cell doses infused. In fact, Prim-MSC contain on average 30% fewer CD34⫹ cells/kg than SS-MSC in autologous transplants and only 20% more CD34⫹ cells in allogeneic transplants. Thus, there must be a “second effect” of G-CSF upon stem cells that enables them to produce more rapid early engraftment. The “second effect” may very well be, in man as it is in mice, differences in integrin expression between BSC and residual Prim-MSC that were produced by mobilization treatment [71]. Cyclophosphamide and G-CSF induce down-

regulation of a2 integrin and upregulation of a5 integrin expression in Prim-MSC in mice. BSC bear significantly lower levels than Prim-MSC of several integrins. These differences are associated with a 50% reduction in marrow homing potential of BSC vis a´ vis Prim-MSC in the mouse model. In addition, human BSC grafts contain 50 to 60% more CD34⫹ cells than G-CSF Prim-MSC. Equal engraftment rates for BSC and Prim-MSC products suggest higher engraftment efficiency for Prim-MSC. Moreover, autologous G-CSF Prim-MSC, collected after failure to mobilize BSC, engrafted rapidly (day ⫹12 for granulocytes and day ⫹13 for platelets) [72]. Finally, the “second effect” may be deciphered from the differential expression of at least 27 genes involved in cell cycle, DNA synthesis, cell-cycle initiation, proapoptosis, and receptors [73]. To conclude, the answer to the original question posed in the abstract of this review is Prim-MSC engraft as rapidly as BSC because of G-CSF treatment before collection. The anatomic site of stem cell acquisition is not the determining factor for pace of engraftment. With the data we have summarized, use of Prim-MSC seems acceptable at the present time. However, we would like to see Prim-MSC studied in direct comparison with BSC.

Acknowledgments The authors gratefully acknowledge the skillful assistance of Ms. Mary Falvey, Deborah Morgan, Kerin DaCruz, Katherine Donohue, and Carol LaRoche, without whose collective efforts this manuscript would not have been possible. This manuscript was supported by National Institutes of Health (NHLBI and NCI) grants RO1HL60528 (RS), RO1-HL73714 (RS), RO1-CA84156 (RS), and by the Adele R. Decof Cancer Center (GJE). There are no potential conflicts for the authors.

References 1. Epstein RB, Graham TC, Buckner CD, Bryant J, Thomas ED. Allogeneic marrow engraftment by cross circulation in lethally irradiated dogs. Blood. 1966;28:692–707. 2. Calvo W, Fliedner TM, Herbst E, Hugl E, Bruch C. Regeneration of blood-forming organs after autologous leukocyte transfusion in lethally irradiated dogs. II. Distribution and cellularity of the marrow in irradiated and transfused animals. Blood. 1976;47:593–601. 3. Goldman JM. Modern approaches to the management of chronic granulocytic leukemia. Semin Hematol. 1978;15:420–430. 4. Ko¨rbling M, Burke P, Braine H, Elfenbein G, Santos G, Kaizer H. Successful engraftment of blood derived normal hemapoietic stem cells in chronic myelogenous leukemia. Exp Hematol. 1981;9:684–690. 5. Ko¨rbling M, Do¨rken B, Ho AD, Pezzutto A, Hunsten W, Fliedner TM. Autologous transplantation of blood-derived hemapoietic stem cells after myeloablative therapy in a patient with Burkitt’s lymphoma. Blood. 1986;67:529–532. 6. Teshima T, Harada M, Takamatsu Y, et al. Cytotoxic drug and cytotoxic drug/G-CSF mobilization of peripheral blood stem cells and their use for autografting. Bone Marrow Transplant. 1992;10:215–220. 7. Kessinger A, Armitage JO, Landmark JD, Smith DM, Weisenburger DD. Autologous peripheral hematopoietic stem cell transplantation

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

8.

9. 10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

restores hematopoietic function following marrow ablative therapy. Blood. 1988;71:723–727. Kro¨ger N, Renges H, Sonnenberg S, et al. Stem cell mobilisation with 16 µ/kg vs 10 µ/kg of G-CSF for allogeneic transplantation in healthy donors. Bone Marrow Transplant. 2002;29:727–730. Horowitz MM. Report on state of the art in blood and marrow transplantation. IBMTR/ABMTR Newsletter. 2002;9:4–11. Le´vesque J-P, Takamatsu Y, Nelsson SK, Simmons PJ. Vascular cell adhesion molecule-1 (CD106) is cleaved by neutrophil proteases in the bone marrow following hematopoietic progenitor cell mobilization by granulocyte colony-stimulating factor. Blood. 2001;98:1289–1297. Le´vesque J-P, Hendy J, Takamatsu Y, Williams B, Winkler IG, Simmons PJ. Mobilization by either cyclophosphamide or granulocyte colony-stimulating factor transforms the bone marrow into a highly proteolytic environment. Exp Hematol. 2002;30:440–449. Petit I, Szyper-Kravitz M, Nagler A, et al. G-CSF induces stem cell mobilization by decreasing bone marrow SDF-1 and up-regulating CXCR4. Nat Immunol. 2002;3:687–693. Lapidot T, Petit I. Current understanding of stem cell mobilization: The roles of chemokines, proteolytic enzymes, adhesion molecules, cytokines, and stromal cells. Exp Hematol. 2002;30:973–981. Vose JM, Sharp G, Wing C, et al. Autologous transplantation for aggressive non-Hodgkin’s lymphoma: Results of a randomized trial evaluating graft source and minimal residual disease. J Clin Oncol. 2002;20:2344–2352. Stoppa AM, Blaise D, Viens P, et al. Phase I study of in vivo lenograstim (rHuG-CSF) for stem cell collection demonstrates improved neutrophil recovery after autologous bone marrow transplantation. Bone Marrow Transplant. 1994;13:541–547. Beyer J, Schwella N, Zingsem J, et al. Hematopoietic rescue after highdose chemotherapy using autologous peripheral blood progenitor cells or bone marrow: A randomized comparison. J Clin Oncol. 1995;13: 1328–1335. Hansen BP, Knudsen H, Gaarsdal E, Jensen L, Ralfkiaer E, Johnsen HE. Short-term in vivo priming of bone marrow haematopoiesis with rhG-CSF, rhGM-CSF or rhIL-3 before marrow harvest expands myelopoiesis but does not improve engraftment capability. Bone Marrow Transplant. 1995;16:373–379. Schmitz N, Linch DC, Dreger P, et al. Randomised trial of filgrastimmobilized peripheral blood progenitor cell transplantation vs autologous bone marrow transplantation in lymphoma patients. Lancet. 1996; 347:353–357. Damiani D, Fanin R, Silvestri F, et al. Randomized trial of autologous filgrastim-primed bone marrow transplantation vs filgrastim-mobilized peripheral blood stem cell transplantation in lymphoma patients. Blood. 1997;90:36–42. Dicke KA, Hood DL, Arneson M, Fulbright L, et al. Effects of shortterm in vivo administration of G-CSF on bone marrow prior to harvesting. Exp Hematol. 1997;25:34–38. Majolino I, Pearce R, Taghipour G, Goldstone AH. Peripheral-blood stem-cell transplantation vs autologous bone marrow transplantation in Hodgkin’s and non-Hodgkin’s lymphomas: A new matched-pair analysis of the European Group for Blood and Marrow Transplantation Registry Data. J Clin Oncol. 1997;15:509–517. Weisdorf D, Miller J, Verfaillie C, et al. Cytokine-primed bone marrow stem cells vs peripheral blood stem cells for autologous transplantation: a randomized comparison of GM-CSF vs G-CSF. Biol Blood Marrow Transplant. 1997;3:217–223. Knudsen LM, Hansen SW, Dauga˚rd G, et al. Comparison of rhG-CSF primed bone marrow and blood stem cell autografts: An analysis of engraftment in malignant lymphomas and solid tumours. Eur J Haematol. 1998;61:229–234. Janssen WE, Elfenbein GJ, Perkins JB. Final report of the first prospective, stratified, randomized trial comparing G-CSF primed bone marrow cells with G-CSF mobilized peripheral blood cells for pace of hematopoietic engraftment and disease free survival after high dose therapy

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

337

and autotransplant. In: Dicke KA, Keating A, eds. Autologous Blood and Marrow Transplantation: Proceedings of the 9th International Symposium. Charlottesville, VA: Carden Jennings; 1999. p. 580–598. Jerjis S, Croockewit S, Muus P, Schaap N, Preijers F, de Witte T. Cost analysis of autologous peripheral stem cell transplantation vs autologous bone marrow transplantation for patients with non-Hodgkin’s lymphoma and acute lymphoblastic leukaemia. Leuk Lymphoma. 1999; 36:33–43. Kanteti R, Miller KB, McCann JC, et al. Randomized trial of peripheral blood progenitor cell vs bone marrow as hematopoietic support for high-dose chemotherapy in patients with non-Hodgkin’s lymphoma and Hodgkin’s disease: A clinical and molecular analysis. Bone Marrow Transplant. 1999;24:473–481. Bensinger WI, Martin PJ, Storer B, et al. Transplantation of bone marrow as compared with peripheral-blood cells from HLA-identical relatives in patients with hematologic cancers. N Engl J Med. 2001; 344:175–181. Couban S, Simpson DR, Barnett MJ, et al. A randomized multicenter comparison of bone marrow and peripheral blood in recipients of matched sibling allogeneic transplants for myeloid malignancies. Blood. 2002;100:1525–1531. Ringden O, Labopin M, Bacigalupo A, et al. Transplantation of peripheral blood stem cells as compared with bone marrow from HLAidentical siblings in adult patients with acute myeloid leukemia and acute lymphoblastic leukemia. J Clin Oncol. 2002;20:4655–4664. Isola LM, Scigliano E, Skerrett D, et al. A pilot study of allogeneic bone marrow transplantation using related donors stimulated with GCSF. Bone Marrow Transplant. 1997;20:1033–1037. Serody JS, Sparks SD, Lin Y, et al. Comparison of granulocyte colonystimulating factor (G-CSF)-mobilized peripheral blood progenitor cells and G-CSF-stimulated bone marrow as a source of stem cells in HLAmatched sibling transplantation. Biol Blood Marrow Transplant. 2000; 6:434–440. Morton J, Hutchins C, Durrant S. Granulocyte-colony-stimulating factor (G-CSF) primed allogeneic bone marrow: Significantly less graftvs-host disease and comparable engraftment to G-CSF-mobilized peripheral blood stem cells. Blood. 2001;98:3186–3191. Ko¨rbling M, Przepiorka D, Huh YO, et al. Allogeneic blood stem cell transplantation for refractory leukemia and lymphoma: Potential advantage of blood over marrow allografts. Blood. 1995;85:1659–1665. Hassan HT, Stockschlader M, Schleimer B, Kru¨ger W, Zander AR. Comparison of the content and subpopulations of CD3 and CD34 positive cells in bone marrow harvests and G-CSF-mobilized peripheral blood leukapheresis products from healthy adult donors. Transpl Immunol. 1996;4:319–323. Bensinger WI, Clift R, Martin P, et al. Allogeneic peripheral blood stem cell transplantation in patients with advanced hematologic malignancies: A retrospective comparison with marrow transplantation. Blood. 1996;88:2794–2800. Pavletic SZ, Bishop MR, Tarantolo SR, et al. Hematopoietic recovery after allogeneic blood stem-cell transplantation compared with bone marrow transplantation in patients with hematologic malignancies. J Clin Oncol. 1997;15:1608–1616. Faucher C, Fortanier C, Viens P, et al. Clinical and economic comparison of lenograstim-primed blood cells (BC) and bone marrow (BM) allogeneic transplantation. Bone Marrow Transplant. 1998;21(Suppl 3):S92–S98. Schmitz N, Bacigalupo A, Hasenclever D, et al. Allogeneic bone marrow transplantation vs filgrastim-mobilised peripheral blood progenitor cell transplantation in patients with early leukemia: First results of a randomized multicentre trial of the European Group for Blood and Marrow Transplantation. Bone Marrow Transplant. 1998;21:995–1003. Vigorito AC, Azevedo WM, Marques JFC, et al. A randomised, prospective comparison of allogeneic bone marrow and peripheral blood progenitor cell transplantation in the treatment of haematological malignancies. Bone Marrow Transplant. 1998;22:1145–1151.

338

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339

40. Mahmoud HK, Fahmy OA, Kamel A, Kamel M, El-Haddad A, Alkadi D. Peripheral blood vs bone marrow as a source of allogeneic hematopoietic stem cell transplantation. Bone Marrow Transplant. 1999; 24:355–358. 41. Szer J, Curtis DJ, Bardy PG, Grigg AP. The addition of allogeneic peripheral blood-derived progenitor cells to bone marrow for transplantation: Results of a randomised clinical trial. Aust N Z J Med. 1999;29:487–493. 42. Blaise D, Kuentz M, Fortanier C, et al. Randomized trial of bone marrow vs lenograstim-primed blood cell allogeneic transplantation in patients with early-stage leukemia: A report from the Socie´te´ Francaise de Greffe de Moelle. J Clin Oncol. 2000;18:537–546. 43. Champlin RE, Schmitz N, Horowitz MM, et al. Blood stem cells compared with bone marrow as a source of hematopoietic cells for allogeneic transplantation. Blood. 2000;95:3702–3709. 44. Powles R, Mehta J, Kulkarni S, et al. Allogeneic blood and bonemarrow stem cell transplantation in haematological malignant disease: A randomized trial. Lancet. 2000;355:1231–1237. 45. Heldal D, Tjønnfjord G, Brinch L, et al. A randomized study of allogeneic transplantation with stem cells from blood or bone marrow. Bone Marrow Transplant. 2000;25:1129–1136. 46. Nivison-Smith JT, Bradstock KF, Szer J, et al. Allogeneic haemopoietic cell transplants in Australia, 1996—A multi-centre retrospective comparison of the use of peripheral blood stem cells with bone marrow. Bone Marrow Transplant. 2001;28:21–27. 47. Guardiola P, Runde V, Bacigalupo A, et al. Retrospective comparison of bone marrow and granulocyte colony-stimulating factor–mobilized peripheral blood progenitor cells for allogeneic stem cell transplantation using HLA identical sibling donors in myelodysplastic syndromes. Blood. 2002;99:4370–4378. 48. Nagatoshi Y, Kawano Y, Watanabe T, et al. Hematopoietic and immune recovery after allogeneic peripheral blood stem cell transplantation and bone transplantation in a pediatric population. Pediatr Transplant. 2002;6:319–326. 49. Ji S-Q, Chen H-R, Wang H-X, Yan H-Ming, Pan Sp, Xun CQ. Comparison of outcome of allogeneic bone marrow transplantation with and without granulocyte colony-stimulating factor (lenograstim) donormarrow priming in patients with chronic myelogenous leukemia. Biol Blood Marrow Transplant. 2002;8:261–267. 50. Elfenbein GJ, Sackstein R, Oblon DJ. Do G-CSF mobilized, peripheral blood–derived stem cells from healthy, HLA-identical donors really engraft more rapidly than do G-CSF primed, bone marrow–derived stem cells? No! Blood Cells Mol Dis. 2004;32:106–111. 51. Smith TJ, Hillner BE, Schmitz N, et al. Economic analysis of a randomized clinical trial to compare filgrastim-mobilized peripheral-blood progenitor-cell transplantation and autologous bone marrow transplantation in patients with Hodgkin’s and non-Hodgkin’s lymphoma. J Clin Oncol. 1997;15:5–10. 52. Kottaridis PD, Peggs K, Schmitz N, et al. Survival and freedom from progression in autotransplant lymphoma patients is independent of stem cell source: further follow-up from the original randomised study to assess engraftment. Leuk Lymphoma. 2002;43:531–536. 53. Elfenbein GJ. Transplantation for high risk breast cancer (editorial)N Eng J Med. 2003;349:80–82. 54. Storek J, Gooley T, Siadak M, et al. Allogeneic peripheral blood stem cell transplantation may be associated with a high risk of chronic graftvs-host disease. Blood. 1997;90:4705–4709. 55. Elfenbein GJ. Clinical factors contributing to the pace of engraftment after allogeneic and autologous stem cell transplantation: Multivariate analyses. In: Abraham NG, Tabilio A, Martelli M, Asano S, Donfransco A, eds. Molecular Biology of Hematopoiesis, vol. 6. New York: Plenum Publishing; 1999. p. 103–111.

56. Elfenbein GJ, Janssen WE, Perkins JB, Partyka JS, Fields KK. Mathematical modeling of human hematopoiesis: Lessons learned from the bedside following autologous peripheral blood stem cell transplants. In: Dicke KA, Keating A, eds. Autologous Blood and Marrow Transplantation: Proceedings of the 8th International Symposium. Charlottesville, VA: Carden Jennings; 1997. p. 443–466. 57. Elfenbein GJ, Janssen WE, Perkins JB. Relative contributions of marrow microenvironment, growth factors, and stem cells to hematopoiesis in vivo in man: Review of results from autologous stem cell transplant trials and laboratory studies at the Moffitt Cancer Center. In: Sackstein R, Janssen WE, Elfenbein GJ, eds. Bone Marrow Transplantation: Foundations for the 21st Century, Annals of the New York Academy of Sciences. vol. 770. New York: The New York Academy of Sciences; 1995. p. 315–338. 58. Lobo F, Kessinger A, Landmark JD, et al. Addition of peripheral blood stem cells collected without mobilization techniques to transplanted autologous bone marrow did not hasten marrow recovery following myeloablative therapy. Bone Marrow Transplant. 1991;8:389–392. 59. Janssen WE, Smilee R, Carter R. Mobilization of peripheral blood stem cells (PBSC): Comparing cyclophosphamide and growth factor based regimens. In: Worthington-White D, Gee A, Gross S, eds. Advances in Bone Marrow Purging and Processing: Prog Clin Biol Res, vol 389. New York: Wiley-Liss; 1994. p. 429–439. 60. Janssen WE, Elfenbein GJ, Fields KK, et al. Comparison of cell collections and rates of post-transplant granulocyte recovery when G-CSF and GM-CSF are used as mobilizers of peripheral blood stem cells for autotransplantation. In: Dicke KA, Keating A, eds. Autologous Blood and Marrow Transplantation: Proceedings of the 7th International Symposium. Arlington, TX: MD Anderson; 1995. p. 527–539. 61. Damiani D, Silvestri F, Fanin R, et al. Does recombinant human granulocyte colony-stimulating factor really prime marrow stem cells in mice and humans? Blood. 1999;93:446–449 (letter). 62. Janssen WE. Mobilization of peripheral blood stem cells for autologous transplantation: Methods, mechanisms, and role in accelerating hematopoietic recovery. In: Sackstein R, Janssen WE, Elfenbein GJ, eds. Bone Marrow Transplantation: Foundations for the 21st Century; Annals of the New York Academy of Sciences, vol 770. New York: The New York Academy of Sciences; 1995. p. 116–129. 63. Poynard T, Munteanu M, Ratziu V, et al. Truth survival in clinical research: An evidence-based requiem? Ann Intern Med. 2002;136:888– 895. 64. Le´onard BM, He´tu F, Busque L, et al. Lymphoma cell burden in progenitor cell grafts measured by competitive polymerase chain reaction: Less than one log difference between bone marrow and peripheral blood. Blood. 1998;91:331–339. 65. Fortanier C, Kuentz M, Sutton L, et al. Healthy sibling donor anxiety and pain during bone marrow or peripheral blood stem cell harvesting for allogeneic transplantation: Results of a randomised study. Bone Marrow Transplant. 2002;29:145–149. 66. Ringden O, Labopin M, Bacigalupo A, et al. Transplantation of peripheral blood stem cells as compared with bone marrow from HLAidentical siblings in adult patients with acute myeloid and acute lymphoblastic leukemia. J Clin Oncol. 2002;20:4655–4664. 67. Exley MA, Tahir SMA, Cheng O, et al. Cutting edge: A major fraction of human bone marrow lymphocytes are Th2-like CD1d-reactive T cells that can suppress mixed lymphocyte responses. J Immunol. 2001; 167:5531–5534. 68. Johnson BD, Konkol MC, Truitt RL. CD25⫹ immunoregulatory Tcells of donor origin suppress alloreactivity after BMT. Biol Blood Marrow Transplant. 2002;8:525–535. 69. Pan L, Delmonte J Jr, Jalonen CK, Ferrara JLM. Pretreatment of donor mice with granulocyte colony-stimulating factor polarizes donor T lymphocytes toward type-2 cytokine production and reduces severity of experimental graft-vs-host disease. Blood. 1995;86:4422–4429. 70. Cornelissen JJ, van der Holt B, Peterson EJ, et al. A randomized multicenter comparison of CD34⫹-selected progenitor cells from

G.J. Elfenbein and R. Sackstein / Experimental Hematology 32 (2004) 327–339 blood vs bone marrow in recipients of HLA-identical allogeneic transplants for hematologic malignancies. Exp Hematol. 2003;31:855–864. 71. Wagers AJ, Allsopp RC, Weismann IL. Changes in integrin expression are associated with altered homing properties of Lin-/lo Thy1.1loSca1⫹c-kit⫹ hematopoietic stem cells following mobilization by cyclophosphamide/granulocyte colony-stimulating factor. Exp Hematol. 2002;30:176–185.

339

72. Phillips GL, Hale GA, Howard DS, et al. G-CSF primed autologous marrow harvest and transplantation in cytapheresis “mobilization failure” patients: a descriptive analysis. Hematology. 2004;5:223–231. 73. Steidl U, Kronenwett R, Haas R. Differential gene expression underlying the functional distinctions of primary human CD34⫹ hematopoietic stem and progenitor cells from peripheral blood and bone marrow. Ann N Y Acad Sci. 2003;996:89–100.