Intravenous busulfan-based conditioning prior to allogeneic hematopoietic stem cell transplantation: Myeloablation with reduced toxicity

Experimental Hematology 31 (2003) 428–434

Intravenous busulfan-based conditioning prior to allogeneic hematopoietic stem cell transplantation: Myeloablation with reduced toxicity Avichai Shimonia, Bella Bieloraib, Amos Torenb, Izhar Hardana, Abraham Avigdora, Moshe Yeshuruna, Isaac Ben-Bassata, and Arnon Naglera a

Departments of Hematology and Bone Marrow Transplantation, and Pediatric Hemato-Oncology, Chaim Sheba Medical Center, Tel-Hashomer, Israel

b

(Received 21 October 2002; revised 27 December 2002; accepted 18 February 2003)

Objective. Allogeneic transplantation is a potentially curative treatment for hematologic malignancies but is associated with a high rate of complications. Busulfan is a common component of pretransplant conditioning but has an erratic and unpredictable bioavailability when administered orally. Intravenous (IV) busulfan was recently introduced into clinical practice. Prior studies showed consistent and predictable drug delivery with tight control of busulfan plasma levels, avoiding over- and under-dosing. This study was designed to define the role of IV busulfan in different transplant and disease settings. Patients and Methods. The study included 43 patients with various hematologic malignancies conditioned with high-dose IV busulfan-containing regimens prior to allogeneic transplantation. The donors were HLA-matched siblings (n ⫽ 24), matched unrelated (n ⫽ 14), or 1antigen mismatched related donors (n ⫽ 5). Outcome parameters were recorded. Results. Forty-two patients had initial engraftment. The toxicity profile was favorable. No patient developed veno-occlusive disease of the liver. Acute graft-vs-host disease (GVHD) grades II–IV occurred in 18 patients (42%). Six patients died of treatment-related causes, five of complications related to acute GVHD, and only one died of organ toxicity. Actuarial non– relapse-related mortality risk was 10% at day 100 and 18% at 2 years posttransplant. The actuarial 2-year overall survival and disease-free survival (DFS) rates were 63% and 44%, respectively. Disease status other than refractory relapse, myeloid disease, and no severe GVHD posttransplant predicted for longer DFS in a multivariant model. Conclusions. IV busulfan-containing regimens allow consistent engraftment of allografts from related and unrelated donors such that myeloablation is administered with a toxicity profile typical of non-myeloablative conditioning. Favorable outcome was seen in patients with myeloid leukemias and in early or intermediately advanced disease; however, this regimen may not be sufficiently cytoreductive in patients with very advanced or active leukemia and in acute lymphoblastic leukemia. IV busulfan merits further study to better define its role as a preferred substitute for oral busulfan in pretransplant conditioning. 쑕 2003 International Society for Experimental Hematology. Published by Elsevier Science Inc.

Allogeneic hematopoietic stem cell transplantation is a potentially curative treatment for a wide range of hematologic malignancies but is associated with a high risk for treatmentrelated complications [1,2]. High-dose busulfan combined with cyclophosphamide has become a widely used regimen for myeloablative conditioning [3]. Oral busulfan has an erratic and unpredictable absorption with wide inter- and also

Offprint requests to: Avichai Shimoni, M.D., Department of Bone Mar row Transplantation, Chaim Sheba Medical Center, Tel-Hashomer, Israel; E-mail: [email protected]

intra-patient variability [4]. A high area under the curve of busulfan plasma concentration vs time is associated with a high-risk of regimen-related toxicity and, in particular, venoocclusive disease (VOD) of the liver [5–8]. Conversely, low busulfan concentrations are associated with a higher risk of graft rejection [6,9–11] and leukemia relapse [9]. Monitoring of busulfan levels and dose adjustments can allow for better control of the dose administered and reduction of these risks, but still in many patients, this cannot be easily achieved [4,8,12,13]. Some researchers have questioned the effectiveness of drug monitoring [14]. IV busulfan was recently

0301-472X/03 $–see front matter. Copyright 쑖 2003 International Society for Experimental Hematology. Published by Elsevier Science Inc. doi: 1 0 .1 01 6 /S 03 0 1 -4 7 2 X( 0 3 )0 0 0 47 - X

A. Shimoni et al. /Experimental Hematology 31 (2003) 428–434

introduced into clinical use [15–18]. It is easier to administer to patients and less associated with VOD of the liver partially due to elimination of first-pass effect through the liver. The initial experience with this product showed that busulfan pharmacokinetics was more predictable, achieving tight control of plasma levels and less need for plasma level testing and dose adjustments [17]. The variability of plasma levels when using fixed IV dosage was less than that expected with level-adjusted oral dosing such that plasma level testing may not be required. Based on these initial studies, we conducted the current study to assess the toxicity profile and outcomes associated with allogeneic transplantation with IV busulfan-based conditioning and to better define the role of IV busulfan in different transplant settings such as from unrelated and mismatched donors and in different diseases and disease status at transplantation.

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and no dose adjustments were done during conditioning [17]. Prophylaxis against graft-vs-host disease (GVHD) consisted of cyclosporine and a short course of methotrexate (15 mg/m2 on day 1 and 10 mg/m2 on days 3 and 6). Granulocyte colony-stimulating factor (G-CSF, 5 mg/kg) was administered routinely until engraftment. The standard institutional regimen of antibiotics was employed for the prevention of bacterial, viral, fungal, and pneumocystis infections. Evaluation of response Neutrophil and platelet engraftment were defined as the first of three days with absolute neutrophil count (ANC) ⬎0.5 × 109/L and the first of 7 days with untransfused platelet count ⬎20 × 109/ L, respectively. Toxicity after transplantation was graded by the Bearman scale [19]. Acute and chronic GVHD were graded and staged by standard criteria. Chimerism was tested with FISH using X and Y probes in sex-mismatched transplants and with PCR analysis of microsatellite markers in sex-matched transplants [20]. Response and relapse were determined by standard hematologic criteria. Cytogenetic and molecular markers were used when applicable but not used for determination of disease status.

Patients and Methods Patient eligibility Patients were eligible for this study if they had any hematologic malignancy at high risk for relapse. Patients with acute myeloid leukemia (AML) could be at first remission but at high risk for relapse due to adverse cytogenetical abnormalities, prior hematological disorder, excessive blast count at presentation (⬎100 × 109/L) or slow response to induction therapy (requiring two or more chemotherapy cycles for remission induction) or at any status beyond first remission. Similar criteria were used for patients with acute lymphoblastic leukemia (ALL). Patients with chronic myeloid leukemia (CML) had to be resistant to interferon and/or imatinib mesylate or beyond chronic phase. Patients with myelodysplastic syndrome (MDS) had to be at least with excess blasts but could be previously untreated. Patients age 1–60 were eligible. Patients were required to be free of marked organ dysfunction and to have an ECOG performance score of 0–1. Patients had to have an HLAcompatible related or unrelated donor willing to donate peripheral blood stem cells or bone marrow. All patients or guardians gave written informed consent, and the study was approved by the institutional review board. Conditioning regimen The conditioning regimen consisted of IV busulfan (Busulfex, Orphan Medical, Minnetonka, MN) administered at 0.8 mg/kg body weight (calculated as the lower of ideal or actual body weight) for 16 doses and cyclophosphamide 60 mg/kg for two doses in adult patients and 50 mg/kg for four doses in pediatric patients. Patients with unrelated or mismatched related donor were given antithymocyte globulin (ATG, Fresenius, Bad, Hamburg, Germany) at 5 mg/ kg for two to three doses. Patients with very extensive recent therapy (n ⫽ 1) or mild cardiac dysfunction (cardiac ejection fraction 40 to 50%, n ⫽ 2) were eligible for a conditioning regimen consisting of fludarabine at 30 mg/m2 for five doses, 16 doses of IV busulfan (0.8 mg/kg each dose), and ATG. Phenytoin was administered before and until 24 hours after completion of busulfan. Based on prior studies showing tight control of busulfan plasma levels when using this regimen, plasma levels were not determined

Statistical analysis Overall survival (OS) was calculated from the day of transplantation until death of any cause or last follow-up. Disease-free survival (DFS) was calculated from the day of transplantation until relapse or death of any cause or last follow-up. The probabilities of survival, relapse, and non-relapse mortality rates were estimated and plotted using the Kaplan-Meier method [21]. The effect of various patient and disease categorical variables on survival and relapse probabilities was studied with the log-rank test. A Cox proportional hazard model was used to determine the significance of multiple variables in determining these outcomes.

Results Patient characteristics Forty-five patients with various hematological malignancies were included in the study. The median age was 31 years (range, 1–58), 30 adults and 13 children (17 years of age and younger), 26 male and 17 female. The disease characteristics and status at transplantation are outlined in Table 1. The donors were HLA-matched siblings (n ⫽ 24), 1-antigen– mismatched related donors (n ⫽ 5), and matched unrelated donors (n ⫽ 14, two with one major HLA antigen mismatch). The allograft source was peripheral blood stem cells (n = 37) or bone marrow (n ⫽ 6). Engraftment Forty-two of 43 patients engrafted. The median time to ANC 0.5 × 109/L was 12.5 days (range, 9–18 days). The median time to platelet 20 × 109/L was 15.5 days (range, 10–32 days; five patients did not achieve platelet transfusion independency). Neutropenia was observed relatively late, median day ⫹4 after transplantation, (range, 0–9) resulting in a median total of 9.5 days in neutropenia (range, 5–15). One

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Table 1. Disease characteristics at transplantation Disease

Number

Myeloid (n ⫽ 36)

Lymphoid (n ⫽ 7)

‡

Risk for relapse (by disease status)

AML

26

MDS* CML

5 4

AMM†

1

ALL

6

NHL

1 45

Disease status at transplantation CR1 (high-risk) Induction failure Untreated 1st relapse CR2 Refractory relapse Previously untreated Chronic phase Accelerated phase Second chronic phase Previously untreated

8 6 2 6 4 5 1 2 1 1

CR1 (high risk) CR2 Refractory relapse Refractory relapse

3 2 1 1

Low Intermediate High

18 19 6

AML, acute myeloid leukemia; MDS, myelodysplastic syndromes (*all these patients were in transformation); CML, chronic myeloid leukemia; AMM, agnogeneic myeloid metaplasia with myelofibrosis (†this patient was in leukemic transformation at transplantation); ALL, acute lymphatic leukemia; NHL, non-Hodgkin’s lymphoma. ‡ Relapse risk was determined by disease status: low-risk, acute leukemia in first remission, CML in chronic phase, MDS previously untreated; intermediate risk, acute leukemia in second remission, untreated first relapse or induction failure, CML beyond chronic phase but not in blast crisis; high-risk, refractory relapse or blast crisis. Low-risk patient with acute leukemia were also at higher risk for relapse than expected in CR1 due to adverse cytogenetic abnormalities, excessive blast count at diagnosis, a prior hematologic disorder, or slow response to therapy.

patient had primary graft rejection but was successfully salvaged with a second transplantation from a different donor. All the patients achieved 100% donor chimerism. Toxicity and GVHD Mucositis occurred in most patients. Liver toxicity as evidenced by elevation of bilirubin and/or transaminases was common. Seventeen patients had grade I–II liver toxicity by the Bearman criteria. None of the patients fulfilled other Jones criteria such as hepatomegaly and/or fluid retention for defining veno-occlusive disease (VOD). Hepatic toxicity was transient, occurring most often after the second dose of methotrexate given for GVHD prophylaxis on day ⫹3 and resolved promptly. Other toxicities included transient grade III renal toxicity (one patient), transient grade I–II cardiac toxicity (two patients), grade I–II hemorrhagic cystitis (five patients), and severe thrombotic thrombocytopenic purpura (one patient). Only one patient died of organ toxicity that may have been related to the conditioning regimen; this was a child with fatal idiopathic pneumonia syndrome 3 months posttransplant. Acute GVHD occurred in 18 patients (42%). Grade II– IV and III–IV acute GVHD occurred in 16 (37%) and seven

(16%), respectively. Chronic GVHD occurred in 18 of 28 evaluable patients (64%), 11 limited, seven extensive. Fifteen patients were not evaluable due to early death (eight patients), insufficient follow-up (four patients), or DLI/immunosuppressive therapy withdrawal for posttransplant relapse (three patients, all developed GVHD following this intervention). Non-relapse mortality occurred in six patients. Five died of complications related to GVHD and one from idiopathic pneumonia. The estimated day-100 and overall non-relapse mortality rates are 10⫾5% and 18⫾7%, respectively. The overall non-relapse mortality risk was 12% and 22% in patients with early and advanced disease (as defined earlier), respectively (p ⫽ NS). Outcome With a median follow-up of 13 months (range, 2–31), 29 patients are alive and 14 have died. Six patients died of treatment-related complications and eight of disease relapse. Twenty-five patients remain alive and disease free. Four of the patients currently alive have relapsed, two of them reentered complete cytogenetic remission with the onset of GVHD after additional immune manipulations such as immunosuppressive therapy withdrawal (one patient) and DLI (one patient). The other two have been given other therapies. The actuarial 2-year OS and DFS rates are 63%⫾8% and 44⫾12%, respectively (Fig. 1). Table 2 outlines the univariable analysis of factors influencing outcome. The status of disease and occurrence of acute GVHD grade III–IV were the most significant predictors of adverse outcome. Patients with refractory relapse at transplantation had grim outcomes due to the high risk for posttransplant relapse with only one of six patients surviving. Similarly, patients with severe acute GVHD had adverse outcomes with only one of seven surviving. DFS of patients with myeloid leukemia (AML, MDS, CML) was better than that of patients with lymphoid

Figure 1. Probabilities of overall survival and disease-free survival after conditioning with myeloablative doses of intravenous busulfan and allogeneic hematopoietic stem cell transplantation from related and unrelated donors in patients with hematologic malignancies.

A. Shimoni et al. /Experimental Hematology 31 (2003) 428–434

431

Table 2. Clinical characteristics in relation to overall and disease-free survival after transplantation* Overall survival Variable Total Age adult ped Disease myeloid lymphoid Relapse risk† high low-inter Donor mud/mm Sib AcGVHD gr III–IV gr 0–II

n

alive

OS

43

29

63 ⫾ 8%

30 13

21 8

66 ⫾ 9% 57 ⫾ 15%

36 7

27 2

6 37

Disease-free survival p value

dis-free

DFS

p value

25

44 ⫾ 12%

NS

18 7

45 ⫾ 14% 46 ⫾ 16%

NS

72 ⫾ 8% 29 ⫾ 17%

0.06

24 1

53 ⫾ 14% 14 ⫾ 13%

0.03

1 28

17 ⫾ 15% 71 ⫾ 8%

0.003

1 24

17 ⫾ 15% 49 ⫾ 13%

0.01

19 24

13 16

64 ⫾ 12% 62 ⫾ 11%

NS

10 15

52 ⫾ 13% 58 ⫾ 11%

NS

7 36

1 28

14 ⫾ 13% 74 ⫾ 8%

0.002

1 24

14 ⫾ 13% 51 ⫾ 13%

0.01

*Survival rates estimated by the Kaplan-Meier method and categorical values compared with log-rank test. † Relapse risk defined in Table 1 (inter, intermediate) Ped, pediatric (age 17 years and younger); mud/mm, matched unrelated and 1-antigen mismatched related; Sib, HLA matched sibling; AcGVHD, acute graft-vs-host disease; gr, grade.

malignancies (ALL, NHL) (Fig. 2). The same was observed when AML/MDS patients were compared with ALL patients (data not shown). This is related to the higher risk for posttransplant relapse in ALL patients. Recipient age and donor type did not impact survival. The factors found significant in the univariable analysis were included in a Cox regression model. This multivariable analysis confirmed the independent impact of each of these factors (Table 3). The estimated relapse risk for the entire group is 32⫾8% and 46⫾14% at 1 and 2 years posttransplant, respectively. The major determinant of relapse risk was the status of disease at transplant reaching 28%, 48%, and 67%

at 2 years posttransplant in patients with low-, intermediate-, and high-risk disease status as defined above (p ⫽ 0.006). The 2-year risk is 39% and 76% in the myeloid and lymphoid malignancies, respectively (p ⫽ 0.05). A Cox regression model confirmed the independent impact of both these factors (Table 4).

Discussion Our study demonstrated that high-dose IV busulfan-containing regimens are tolerable, have a favorable toxicity profile, and improved short- and long-term outcomes. IV busulfan was only recently introduced into clinical use, and Table 3. Proportional hazards regression model for survival and disease-free survival after transplantation* Overall survival

Variable Disease type (lymhoid) Relapse risk† (high) AcGVHD (grade III–IV)

Figure 2. Probabilities of disease-free survival as determined by disease morphology. Myeloid: AML, myelodysplastic syndrome, CML, other chronic myeloproliferative disorders; Lymphoid: ALL, non-Hodgkin’s lymphoma.

Disease-free survival

Hazard ratio Hazard ratio (95% confidence (95% confidence interval) p value interval) p value

2.5 (0.8–7.8)

NS

3.5 (1.2–9.9)

0.02

4.2 (2.0–8.9)

0.001

3.3 (1.8–6.3)

0.001

8.3 (2.5–27.6)

0.001

14.5 (3.4–61.3) 0.001

*The factors found significant in the univariable analysis (Table 2) were included in a Cox regression model. Hazard ratio for reduced survival of categorical variable in parenthesis. † Relapse risk defined in Table 1. AcGVHD, acute graft-vs-host disease.

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Table 4. Proportional hazards regression model for relapse after transplantation* Relapse Risk

Variable Age (adult)

Relapse incidence (number relapses/total in subgroup)

adult 9/30 (30%) ped 3/13 (23%) Disease type lymphoid 4/7 (57%) (lymphoid) myeloid 8/36 (22%) high 4/6 (67%) Relapse risk† (high) low-inter 8/37 (22%) Donor mud/mm 7/19 (37%) (mud/mm) sib 5/24 (21%) AcGVHD gr III–IV 2/7 (29%) (Grade III–IV) gr 0–II 10/36 (28%) Total 12/43 (28%)

Hazard ratio (95% confidence interval) p value 3.9 (0.4–39.0)

NS

10.9 (1.3–13.2)

0.03

2.7 (1.3–5.5)

0.009

1.9 (0.5–3.9)

NS

1.8 (0.2–13.2)

NS

*The factors evaluated in Table 1 were included in a Cox regression model. Hazard ratio for increased relapse risk of categorical variable in parenthesis. † Relapse risk defined in Table 1 (inter, intermediate). Ped, pediatric (age 17 years and younger); mud/mm, matched unrelated and 1-antigen mismatched related; Sib, HLA matched sibling; AcGVHD, acute graft-vshost disease; gr, grade.

data relating to the indications and expected outcomes in different settings are beginning to emerge [15–18]. Anderson et al. reported a pivotal phase II study. In a detailed pharmacokinetics study, they demonstrated high inter- and intrapatient consistency after IV administration [17]. Eighty-six percent of patients maintained the target AUC between 800 and 1500 µMol-min with no dose adjustments. This is a tighter control of busulfan levels than is generally achieved with level-adjusted oral dosing. IV busulfan-containing regimens allowed in our study consistent engraftment of allografts from fully matched or 1antigen–mismatched related donors as well as from unrelated donors. The study of Anderson et al [17] did not include unrelated donor transplants. Prior studies with oral busulfan raised concern that this regimen may not be immunosuppressive enough to allow engraftment of mismatched and unrelated donor grafts, especially in young children [6,10–11,22– 24]. A correlation has been observed between low busulfan plasma levels and graft rejection [6,9–11]. A higher AUC is needed for acceptance of unrelated and mismatched grafts, and when busulfan plasma levels are not tightly controlled, a significant portion of transplant recipients may not reach this level. Treatment-related mortality was limited, reaching 10% at day 100 and 18% at 2 years posttransplant. Only one patient died of idiopathic pneumonia that could have been related to regimen-related organ toxicity. The IBMTR reported among patients with early leukemia 1-year TRM of 17% (in patients age ⬍20 years) to 30% (in patients age ⬎50) for sibling transplants and 35–40% for unrelated donor transplants [25]. Among our 18 early leukemia patients, the

expected age- and donor- adjusted TRM is 28% but was 12% only. Although this is not a direct case-control comparison, these results are encouraging, especially in the unrelated donor setting. VOD is the most serious complication of high-dose busulfan regimens. The incidence of VOD varies widely between reports ranging from 5% to 60%, with severe VOD observed in approximately 10% of transplants [26– 31]. Although we observed a significant rate of moderate hepatic toxicity, none of the patients in this study fulfilled the Jones criteria for VOD [32]; hepatic toxicity was transient and resolved promptly with no related deaths. Prior studies showed a correlation between high busulfan exposure and regimen-related toxicity [5–8]. Tighter level control with the IV formulation is probably related to reduced toxicity. In addition, avoidance of the first-pass effect through the liver may also be associated with the reduced risk for VOD [18]. The increased systemic exposure resulting from the elimination of hepatic first pass effect did not result in excessive pulmonary or central nervous system toxicity as might have been predicted. The rate of severe GVHD in this study, considering the relatively large number of unrelated and mismatched transplants, seems reduced. This was also suggested in other studies [33]. Acute GVHD is related in part to tissue injury and cytokine release [34–35], and limitation of tissue injury with this regimen may have contributed to this observation. However, severe acute GVHD remains a major obstacle to transplant success and better methods for GVHD prevention with preservation of anti-leukemia effects need to be explored. Disease recurrence remains the major cause of treatment failure. The status of disease at transplantation was the major predictor for relapse. The 2-year projected relapse risk ranged from 28% in early leukemia to 67% in refractory relapse. Although we had a relatively small number of ALL patients, the results in this subgroup were inferior due to increased relapse risk even when considering disease status in a multivariant model (Table 4). In some studies of ALL patients, TBI had an advantage over busulfan-based regimens [36,37]. More intensive conditioning regimens may be required in ALL as well as in advanced and refractory leukemia. Altogether, the OS and DFS rates in this study were 63% and 44%, respectively. These results are encouraging considering the high-risk patient population and the donor allograft sources. The improved outcome is related to reduction of toxicity such that myeloablation could be administered with the toxicity profile and engraftment kinetics typical of reduced intensity or non-myeloablative conditioning [38– 39]. In the largest study of non-myeloablative conditioning using the least intensive regimen consisting of 200 rad TBI with or without fludarabine, the Seattle cooperative group reported non-relapse mortality rates of 6% and 22% at day 100 and 2 years, respectively [40]. Notwithstanding that these are different patient groups and not a direct comparison,

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the results are very similar to the 10% and 18% rates in our study. Larger studies are needed to better define the role of IV busulfan before it is accepted as the preferred substitute for the oral formulation. It is currently unknown what will be the role of drug level monitoring when using IV busulfan. The administration of busulfan intravenously markedly reduced the variability in bioavailability. However, drug monitoring with dose adjustments may allow even tighter control of busulfan exposure. This may allow optimizing and increasing, if necessary, busulfan dose for better myeloablation while preventing toxic levels and retaining the favorable toxicity profile. This approach may be particularly useful in patients with advanced or refractory malignancies where there is a relatively high relapse risk with the current regimen.

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