Graft Failure

CHAPTER 23

Graft Failure RONI TAMARI, MD

Graft failure is a life-threatening complication after allogeneic hematopoietic stem cell transplantation (alloHSCT). It was one of the major causes of treatment failure in the early era of allo-HSCT1,2; however, now a days, this complication is less prevalent, probably partly due to improved human leukocyte antigen (HLA) typing techniques, but when occurs, it remains a devastating complication after transplantation with very poor outcomes.3,4

DEFINITIONS Graft failure (GF) after allo-HSCT is a complex syndrome characterized by pancytopenia and hypocellular or acellular bone marrow. Graft failure can be defined based on the mechanism leading to it or the timing of the event. Graft rejection (GR): The best characterized form of graft failure is immune-medicated rejection. In this process, preexisting anti-HLA antibodies5,6 or residual host T lymphocytes eliminate the donor stem cells, and typically these patients have only host cells.7,8 Poor graft function (PGF): This entity is characterized by the presence of full donor engraftment with hypocellular or acellular marrow and varies with the level of pancytopenia. This is due to qualitative or quantitative deficiencies or damage to the hematopoietic stem cells. Primary graft failure: Characterized by the absence of initial donor cell engraftment; the patient never recovers from the neutropenia (absolute neutrophil count < 0.5 × 109/L) induced by the conditioning regimen. Secondary graft failure: Defined as loss of donor cells after initial engraftment occurred. 

GRAFT REJECTION Different immunological mechanism may result in GR. Most commonly it is due to immune recipient T cells, although natural killer (NK) cells-mediated rejection has also been demonstrated in animal models.9–13 Whether antibodies can cause rejection is controversial,14–18 although some data suggest that pretransplant donor-specific antiendothelial precursor cell antibodies augment the risk of GR in clinical allo-HSCT.19 These

studies indicate that cellular mechanisms are the major contributors to graft failure, but humoral mechanisms may also be important. Olsson et al.20 studied retrospectively 967 patients who underwent first allo-HSCT at a single center for various malignant and nonmalignant hematologic disease and reported the incidence of primary and secondary graft failure to be 5.6%, most of them being secondary GF, with primary GF reported only in six patients (0.6%). The following factors were found to be associated with increased risk for GF: (1) transplant after the year 2000 (6%–7%) compared with the ones performed previously (3%) P = .05, and (2) transplantation for nonmalignant disorders had a three times higher incidence of GF than those performed for malignant disease. In patients with malignant diseases, the incidence of GF was 20% for nonhematological malignancies, 10% in both chronic lymphocytic leukemia (CLL) and myeloproliferative disorders (MPDs)/myelofibrosis and 5% in myelodysplastic syndrome, whereas the incidence of GF was lower (2%–3%) in patients with acute leukemia. The intensity of the conditioning regimen was also an important factor in the risk for GF with 8% incidence of GF in patients who received a reduced intensity conditioning (RIC) and 19% in those who had a nonmyeloablative conditioning (NMA), in contrast to only 3% GF observed in patients who received a myeloablative conditioning (MAC). In multivariate analysis, patients conditioned with NMA (relative risk (RR), 4.5; P < .01) or RIC (RR, 2.58; P < .01) had a higher risk for GF than those treated with MAC. Stem cell source was also an important risk factor with higher incidence in recipients of cord blood transplants (CBTs) (18%) than peripheral blood stem cells (PBSCs) (5%) or bone marrow (BM) graft (6%), though this did not reach statistical significance (P = .08). In univariate analysis, both HLA and ABO mismatch between the patient and the donor were associated with increased incidence of GF. This was mostly pronounced for HLAmismatched grafts, and in multivariate analysis, both transplant from a matched unrelated donor (MUD) and HLA-mismatched grafts had markedly increased

Hematopoietic Cell Transplantation for Malignant Conditions. https://doi.org/10.1016/B978-0-323-56802-9.00023-7 Copyright © 2019 Elsevier Inc. All rights reserved.

321

322

SECTION VI  Complications, Infectious Disease, and Special Populations

risk of GF. Moreover, GF rates were similar in 8 out of 8 or 6 out of 6 HLA-matched donor pairs (P = .23), and ABO incompatibility was almost a significant risk factor for GF in a multivariate analysis (RR, 1.36; P = .06). Cell dose was also a risk factor for GF, with risk of 10% in patients with a cell dose below 2.5 × 108 nucleated cells/kg compared with 5% in patients who received a higher cells dose. Patients with a CD34+ cell dose below 3 × 106/kg had an incidence of GF of 12%, which was significantly higher than the 1%–7% risk seen in patients who received a higher cell dose. Graft-versushost disease (GVHD) prophylaxis with cyclosporine A (CsA) and methotrexate (MTX) were associated with a GF rate of 3%, which was lower than that of all other GVHD prophylaxis regimens (P < .001). In a multivariate analysis, there was a tendency for increased risk of GF using CsA and prednisolone (RR, 2.43; P = .05), and the risk was markedly increased using an ex vivo T-depleted graft (RR, 8.92; P < .001). In a large and comprehensive retrospective analysis through the Center for Blood and Marrow Transplantation21 in patients who received a MAC only including 23,272 allo-HSCTs between 1995 and 2008, GF was reported in 1278 patients (5.5%). This analysis looked into patient, disease, and transplant-related factors with relation to GF. Patient-related factors included younger age (<30 years) (odds ratio [OR] = 0.75; P < .001), female to male gender mismatch (OR = 1.28; P = .001), and Karnofsky/Lansky score < 90% (OR = 1.18; P = .042) as associated with increased risk. Disease-related factors included the diseases CLL (OR = 1.57; P = .003) and

chronic myeloid leukemia (CML) (OR = 1.88; P < .001) in comparison to acute myeloid leukemia (AML). In myelodysplastic syndrome (MDS) and myeloprolifective disorder (MPD) the risk for GF was dependent on the presence of absence of splenomegaly (MDS: OR = 2.34, P = .002; MPD: OR = 3.92, P = .001), whereas after splenectomy, patients with MDS and MPD did not have an increased risk for GF. In AML, acute lymphoblastic leukemia, and CML, the incidence of GF was higher in patients with advanced disease (OR = 1.54; P < .001). Transplant-related factors included busulfan/cyclophosphamide (Bu/Cy) as associated with increased risk for GF compared with total-body irradiation (TBI) and Cy (TBI/Cy) (OR = 1.35; P = .002). Well MUDs were associated with GF when compared with matched related donors (OR = 1.38; P < .001), and the highest risk for GF was seen in mismatched donors (OR = 1.79; P < .001). Major ABO mismatch was also associated with increased risk for GF (OR = 1.24; P = .012) as well as BM graft compared with PBSC (7.3% vs. 2.5%, P < .001). Total nucleated cell dose ≤ 2.4 × 108/kg was associated with GF (OR = 1.39; P < .001). Irrespective of graft source, cryopreservation was associated with GF (OR = 1.43; P = .013). GVHD prophylaxis with tacrolimus and MTX was associated with lower risk for GF (OR = 0.61; P < .001) in comparison to CsA/MTX. Interestingly ex vivo and in vivo T-cell depletion of the graft was not associated with increased risk of PGF, suggesting that the intensity of the conditioning regimen probably has a role in overcoming the immune-medicated GR. The findings of this large analysis are summarized in Table 23.1.

TABLE 23.1

Multivariate Risk Model for GF in a Cohort of Patients Who Underwent MAC Allo-HCT and Reported to the CIBMT Between 1995 and 200821 N

OR

<30 years

9440

1

≥30 years

13,815

0.75

Variable

Lower

Upper

Recipient age (years)

P Value <0.001

0.65

0.86

Donor/recipient gender match

<0.001 <0.001

Other

18,166

1

Female/male

4976

1.28

1.1

1.49

0.001

Unknown

113

1.39

0.64

2.99

0.406

Karnofsky/Lansky score (%)

0.005

≥90

16,431

1

<90

5634

1.18

1.01

1.38

0.042

Unknown

1190

0.69

0.49

0.96

0.03

CHAPTER 23  Graft Failure

323

TABLE 23.1

Multivariate Risk Model for GF in a Cohort of Patients Who Underwent MAC Allo-HCT and Reported to the CIBMT Between 1995 and 200821—cont’d N

OR

AML

8296

1

ALL

5758

1.12

0.9

1.39

0.299

CLL

843

1.57

1.17

2.1

0.003

CML

5771

1.88

1.57

2.25

<0.001

MDS

2126

1.38

1.07

1.79

0.013

MPD

461

1.81

0.97

3.39

0.062

Variable

Lower

Upper

Disease

P Value <0.001

Disease status: AML/ALL/CML

<0.001

Early

10,203

1

Intermediate

5534

0.98

0.84

1.15

0.816

Advanced

3746

1.54

1.25

1.89

<0.001

Unknown

342

0.85

0.52

1.4

0.533

Normal

181

1

Splenectomy

91

1.68

0.58

4.87

0.341

Splenomegaly

161

3.92

1.79

8.55

0.001

Unknown

28

0.82

0.1

6.76

0.854

Spleen status: MPD

<0.001

Spleen status: MDS

0.007

Normal

1671

1

Splenectomy

89

1.68

0.77

3.65

0.193

Splenomegaly

174

2.34

1.36

4.03

0.002

Unknown

192

1.5

0.84

2.66

0.167

TBI Cy and other

11,905

1

Bu Cy and other

7778

1.35

1.11

1.65

0.002

Bu and other

1400

1.19

0.87

1.62

0.285

Melphalan and other

166

1.27

0.6

2.66

0.533

TBI and other

1418

1.3

0.98

1.73

0.069

Unknown dosage

588

1.6

0.98

2.61

0.06

Conditioning regimen

0.018

HLA match status

<0.001

Related • HLA identical sibling

10,059

1

• Well matched

7439

1.38

1.15

1.64

<0.001

• Partially matched

3686

1.29

1.05

1.6

0.018

• Mismatched

1829

1.79

1.41

2.27

<0.001

• Unknown

242

1.79

1.09

2.94

0.021

Unrelated

Continued

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SECTION VI  Complications, Infectious Disease, and Special Populations

TABLE 23.1

Multivariate Risk Model for GF in a Cohort of Patients Who Underwent MAC Allo-HCT and Reported to the CIBMT Between 1995 and 200821—cont’d N

OR

Matched

10,821

1

Major

5584

1.24

1.05

1.46

0.012

Minor

4327

1.04

0.85

1.27

0.693

Unknown

2523

1.35

1.07

1.71

0.013

Variable

Lower

Upper

ABO incompatibilities

P Value 0.01

Graft type

<0.001 Splenomegaly

161

3.92

1.79

8.55

0.001

Unknown

28

0.82

0.1

6.76

0.854

Normal

1671

1

Splenectomy

89

1.68

0.77

3.65

0.193

Splenomegaly

174

2.34

1.36

4.03

0.002

Unknown

192

1.5

0.84

2.66

0.167

Spleen status: MDS

0.007

Conditioning regimen

0.018

TBI Cy and other

11,905

1

Bu Cy and other

7778

1.35

1.11

1.65

0.002

Bu and other

1400

1.19

0.87

1.62

0.285

Melphalan and other

166

1.27

0.6

2.66

0.533

TBI and other

1418

1.3

0.98

1.73

0.069

Unknown dosage

588

1.6

0.98

2.61

0.06

HLA match status

<0.001

Related • HLA identical sibling

10,059

1

• Well matched

7439

1.38

1.15

1.64

<0.001

• Partially matched

3686

1.29

1.05

1.6

0.018

• Mismatched

1829

1.79

1.41

2.27

<0.001

• Unknown

242

1.79

1.09

2.94

0.021

Matched

10,821

1

Major

5584

1.24

1.05

1.46

0.012

Minor

4327

1.04

0.85

1.27

0.693

Unknown

2523

1.35

1.07

1.71

0.013

Unrelated

ABO incompatibilities

Graft type

0.01

<0.001

AML, acute myeloid leukemia; Bu, busulfan; CML, chronic myeloid leukemia; CLL, chronic lymphocytic leukemia; Cy, cyclophosphamide; GF, graft failure; HLA, human leukocyte antibody; MPD, myeloproliferative disorder; OR, odds ratio; TBI, total-body irradiation.

CHAPTER 23  Graft Failure

325

Cumulative incidence of rejection CUMULATIVE INCIDENCE (95% CI)

1.0 Matched or permissive: Non-permissive GvH: Non-permissive HvG:

0.8

N = 45; E = 2 N = 10; E = 1 N = 17; E = 4

0.6 Non-permissive HvG vs. Matched or permissive: P < .05 0.4 Non-permissive HvG: 26% (11-60) 0.2

Non-permissive GvH: 10% (16-64) Matched or permissive: 7% (2-26)

0.0 0

12

24

36

48

60

MONTHS AFTER TRANSPLANTATION FIG. 23.1  The probability of graft rejection based on HLA-DPB1 match status.25 Patients and donors

were classified as follows: (1) matched for HLA-DPB1 or with a permissive mismatch (solid line; n = 45); (2) matched for HLA-DPB1 with nonpermissive DPB1 mismatches in HvG direction (broken line; n = 17); (3) matched for HLA-DPB1 with nonpermissive DPB1 mismatches in GvH direction (dotted line; n = 10).CI, confidence interval; HLA, human leukocyte antibody; HvG, host-versus-graft.

This analysis highlights various factors associated with risk of GF, some modifiable and some not. The diseases that were associated with higher risk for GF where diseases that usually require chemotherapy of low- or moderate-intensity pretransplant such as CLL and CML. The association between GF and MPD has been well recognized22–24 and is probably multifactorial and includes a very distorted and fibrosed BM stroma, as well as splenomegaly and potentially allogenic immunization after multiple transfusions. The use of pretransplant treatment with JAK inhibitors may reduce the risk for GF due to its effects on splenomegaly and need for transfusions before allo-HSCT. The conditioning regimen given before the infusion of the stem cells has to be tailored to the purpose of the BM transplantation. However, it always needs to be immunosuppressive and “space creating” to allow the donor cells to engraft. The numbers of functional T lymphocytes remaining in the host and present in the graft have reciprocal effects on GR (host-versus-graft) and GVHD. The higher incidence of GF in younger patients as reported by Olsson et al.21 is likely reflecting a more robust immunity in children and young adult recipients than that in older patient population. HLA compatibility between donor and recipient is of major importance of predicting GF. Olsson’s

analysis highlights that having a transplant from an unrelated donor, even if well matched, was associated with increased risk for GF. When assessing for HLAmatched donor, match for HLA-A, HLA-B, HLA-C, and HLA-DRB1 (8/8 match) is mostly being done or at times also including HLA-DQ (10/10 HLA match). With that, more than 80% of well-matched donors are mismatched at DPB1. Fleischhauer et al.25 reported on transplant outcomes in pediatric population who underwent allo-HSCT for thalassemia, where 10% (7 patients) of the study population had GF. None of the 7 patients were matched for both HLA-DPB1 alleles; 2 patients had permissive DPB1 mismatches, and 5 patients had nonpermissive HLA-DPB1 mismatched donors. The overall cumulative incidence of rejection in this group was 19% (95% confidence interval [CI], 9–43). Interestingly, in four of these cases, the mismatch was in host-versus-graft (HvG) direction, resulting in a significantly higher cumulative incidence of rejection in the HvG group (26%; 95% CI, 11–60) than that in the GvH group (10%; 95% CI, 2–64) (Fig. 23.1). The impact of donor-specific antibodies (DSAs) on outcomes after transplantation has been extensively described in solid organ transplantation where HLA matching is not as important as that in allo-HSCT.26 The presence of DSAs was described as a cause for GF

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SECTION VI  Complications, Infectious Disease, and Special Populations

TABLE 23.2

Summary of Studies Reporting on the Incidence of DSA and Its Effect of GF Allo-HSCT Conditioning

Anti-HLA %

DSA %

Graft Failure With/ Without DSA

Mismatched unrelated

RIC

ND

9

24 versus 1%

592

10/10 and 9/10 unrelated

MAC or RIC

19.6

1.4

37.5 versus 2.7%

Yoshihara et al.74

79

Haploidentical

RIC

20.2

14

27 versus 3%

Ciurea et al.6

24

Haploidentical

RIC

ND

21

60 versus 5%

345

Haploidentical

MAC

25.2

11.3

61% (MFI > 10,000) versus 3.2%

Ciurea et al.6

122

Haploidentical

Nonspecified

ND

18

32 versus 4%

Takanashi et al.28

386

Single CBU

MAC

23.1

5

83 versus 32%

Reference

Patients (n)

Spellman et al.5

115

Ciurea et al.6

Chang

et al.75

Cutler et al.

34

Stem Cell Source

73

Double CBU

MAC or RIC

ND

24

57 versus 5.5%

Ruggeri et al.30

294

Single and double CBU

RIC

23

5

81 versus 44%

Yamamoto et al.76

175

Single CBU

MAC or RIC

39.4

ND

50% if anti–HLA-C, DP, DQ, DRB1/2/3 versus 16%

Allo-HSCT, allogeneic hematopoietic stem cell transplantation; DSA, donor-specific antibody; GF, graft failure; HLA, human leukocyte antibody; MAC, myeloablative conditioning; MFI, median level of fluorescence intensity; RIC, reduced intensity conditioning; ND, not detected; CBU, cord blood unit.

in animal models of allo-HSCT. In a case control study, Spellman et al.5 compared the presence of DSA among 37 patients who had primary GF to 78 controls, all received transplant from an unrelated donor. Among the patients with GF, 9 patients (24%) had DSA, of which 3 had it against class I HLA only, 4 against class II HLA only, and 2 against class I and II. In the control group, there was only 1 case of presence of DSA (against class I and II). This study found that the presence of DSA in the host against class I, II, or both before transplantation is significantly associated with GF. With the increased use of mismatched grafts, whether using a haploidentical donor, mis-MUD, or CBT, data are emerging on the importance of DSA as a risk factor for GF. Table 23.2 summarizes the incidence of presence of anti-HLA antibody and DSA and association with GF among several cohort of CBT and haploidentical transplants.27 In retrospective studies, the incidence of anti-HLA antibodies in CBT recipients varies from 15% to 41%,28–32 and they are more commonly encountered in parous female patients. However, only a minority of patients with anti-HLA antibodies have DSAs with specificity against the CB graft(s). The incidence of preformed DSAs in single CBT is estimated as 5.2%–6.4%28,30

and 3.8%–24.7% in double CBT.29,30,33 Ruggeri et al.30 reported on the presence of DSA in 294 recipients of cord blood RIC transplant. Sixty-two patients (21%) had anti-HLA antibodies, and 14 were positive against the cord blood unit (DSA+). The cumulative incidence of engraftment was 77% in DSA-negative and 44% for DSA-positive patients (P = .003). The median level of fluorescence intensity (MFI) was 3900, and the intensity of the DSA measured by MFI was associated with graft failure. Of the 14 patients with DSA, 6 were engrafted and their median MFI was 2474 (1226– 3650), whereas the median MFI among the 8 who were not engrafted was 7750 (2032–19,969). Cutler et al. reported similar findings in a cohort of 73 patients who underwent double CBT using an RIC or MAC conditioning regimen.34 In contrast to what is mentioned previously, two other large centers have shown no discernible effect of anti-HLA antibodies or DSAs against one or both units on engraftment, unit dominance, or clinical outcomes after dCBT, with no MFI threshold effect.29,32 These conflicting findings may be explained by differences in transplantation practices between centers including conditioning regimens and immunosuppression, including the use of in vivo T-cell depletion. In support of this hypothesis, a recent study suggested

CHAPTER 23  Graft Failure that the presence of DSAs correlates with the presence of cytotoxic T lymphocytes with specificity against the same HLA antigens as the DSAs that might mediate GR.35 How to best incorporate the information about the presence and intensity of DSAs in the CB graft selection process requires further studies. In haploidentical allo-HSCT with posttransplant cyclophosphamide (PTCy), Ciurea et al.36 found that GF occurred in 75% of recipients with DSA compared with 5% of recipients without DSA and that antibodies to HLA-DRB1 were most frequent. Also in haplo-BMT with PTCy, Gladstone et al. 37 found that HLA-directed DSA occurred in 14.5% of all patients and 42% of women undergoing haplotransplant evaluation. DSA can be quantified by the solid phase immunoassay (SPI) using fluorescent beads coated with single phenotype and single-HLA antigens. SPI results can be correlated with cross-matching by flow cytometry or complement-dependent cytotoxicity assays and can be used as a “virtual crossmatch.38 In subsequent analyses from Ciurea and colleagues39 the overall incidence of DSA in haplo-BMT assessments was 18%; 32% of patients with DSA rejected their grafts. Median DSA MFI was 10,055 for patients who rejected versus 2065 for those who engrafted. In their study, graft failure was associated with a complement assay that detects C1q-binding DSA, with only one C1q-negative patient (who had an MFI of 6265) failing to engraft. Patients with C1q-binding DSA also had a higher median MFI of 15,279 versus 2471 for C1q-negative patients. All male patients were C1q-negative, and their median MFI levels were much lower. Pregnancy was associated with a much higher risk of developing DSA than transfusion of blood products. In an algorithm suggested by McCurdyn and Fuchs,40 it is recommended to avoid donors to which the recipient has antidonor HLA antibodies, particularly for levels compatible with a positive complement-dependent cytotoxicity or flow cytometric crossmatch. 

POOR GRAFT FUNCTION PGF is a very different entity from GR, and it is characterized by evidence of donor engraftment, but with poor peripheral blood counts.41 PGF occurs in 5%–27% of patients undergoing allo-HSCT,42 and the severe form is associated with high morbidity and mortality due to infectious and hemorrhagic complications.43 A number of factors are associated with PGF: (1) inadequate stem cell dose due to poor harvest/collection; (2) stem cell damage during ex vivo manipulation or storage; (3) mismatched donor; (4) GVHD44; (5) infections or

327

medications used to treat an infection or noninfectious medications; and (6) use of a T-cell–depleted graft.45 PGF can be primary with suboptimal recovery of blood counts after the initial HSCT or secondary with decreasing blood counts after successful and prompt hematopoietic engraftment. PGF can be a transient event secondary to a reversible insult, such as an acute infection/sepsis or drugs, and blood counts can recover after removal of the insult. However, persistence of low blood counts requires further intervention, either in the form of a second transplant or infusion of more stem cells without further preinfusion conditioning therapy. Tamari et al.46 presented the outcomes of 182 patients who underwent ex vivo T-cell–depleted transplant (TCD) between 1997 and 2012 and reported a cumulative incidence of PGF of 18% at 1 year after transplantation (Fig. 23.2). Infections and antiviral therapies were the most common etiologies for PGF (87%), followed by GVHD, medications related, and unknown etiology in one case. It is important to note that although infections and antiviral therapies were the most common etiologies for PGF, treating the infection did not always result in improvement in graft function. At the time of analysis, 36% of patients who were diagnosed with PGF died from either infectious complications or GVHD, 33% patients had recovery of blood counts either after treatment of an identified offending agent (mostly viral infection) or discontinuation of medications, 15% had counts recovery after further cellular treatment (a TCD stem cell boost), 10% had persistent PGF, and in 6%, there was evidence of relapsed disease. 

CLONAL HEMATOPIESIS AND GRAFT FAILURE Clonal hematopoiesis (CH) resulting from an expansion of cells that harbor an initiating driver mutation has been recently shown to be an aspect of the aging hematopoietic system. There are limited data about CH among allo-HSCT donors and its impact on transplant outcomes. The risk of donor cell leukemia (DCL) has been reported in about 0.1% of allo-HSCT, and Gondek et al.47 recently reported on two cases of DCL and demonstrated that it evolved from CH in the donor cells. Gibson et al.48 studied a group of patients with unexplained cytopenia after allo-HSCT in the absence of evidence of disease relapse. They identified 89 patients (16%) of their transplant cohort, in whom a small group (6 patients, 7%) had “unexplained” cytopenia. Five of the six patients were found to have mutation in DNMT3A, which was confirmed to be of

328

SECTION VI  Complications, Infectious Disease, and Special Populations

FIG. 23.2  Cumulative incidence of poor graft function (PGF) in patients who underwent a T-cell–depleted

transplant.46

donor origin. In contrast, 24 of 84 patients (29%) with “explained” cytopenia after transplantation underwent next-generation sequencing as part of their evaluation, which was negative in all cases. It is important to note, however, that donor age was significantly higher in the group with “unexplained” cytopenia (median age 55 vs. 30 years, P < .0001). This observation requires validation in a larger cohort of patients-donor paired samples; however, this may suggest that donor screening for CH is important, particularly donors older than 50 years. 

TREATMENT Graft Rejection After GR, a second stem cell transplant represents the best chance of long-term, disease-free survival for these patients. Achieving stable engraftment in patients who undergo a second transplant after GR is often difficult with engraftment rates as low as 33% reported in the literature.49 Schreiber et al.4 reported on a cohort of 122 patients who underwent a second allo-HSCT for GF and reported dismal outcomes with OS of only 11% at 1 year after second allo-HSCT. The engraftment rate at day 28 and 100 after second allo-HSCT was 66% and 74%, respectively. The most common causes of death were directly related to BM failure, such is infection and

bleeding. Interestingly, even among the patients who have engrafted, the OS was dismal, 19%, highlighting the general poor prognosis of this patient population. The key to success when planning a second transplant after GR is deep elimination of residual host immunity. Other considerations that need to be taken into account when planning a second transplant is the toxicity associated with the conditioning regimen because the second transplant is usually performed in proximity to the first transplant. Therefore, a strong immune ablative regimen which has a low-toxicity profile is needed. Chewning et al.50 reported on 16 patients who underwent second allo-HSCT at a median of 45 days after GF secondary to GR. All patients, other than one (15 out of 16) had fludarabine-containing regimen: (1) fludarabine/anti thymocyte globulin­ (ATG) (N = 1), (2) fludarabine/Cy (N = 2), (3) fludarabine/Cy/ATG (N = 7), (4) fludarabine/thiotepa/ATG (N = 3), and (5) fludarabine/Thiotepa/CAMPATH (N = 2). One patient had a regimen of Cy/thiotepa/campath. The second transplant was unmodified in 8 patients, and a TCD graft was used in the rest of the patients. After the second transplant, all 16 patients engrafted in a median time of 12 days (range: 9–21 days). The OS at 3 years after second transplant was 35%. The median survival time was 44 days for the remaining patients (N = 10); 6 patients died within 100 days after second allo-HSCT, mostly from infectious causes. This small retrospective

CHAPTER 23  Graft Failure study demonstrated that all patients were able to achieve engraftment and that the cytoreduction was relatively well tolerated with no acute organ failure from toxicity, including no cases of veno-occlusive disease or grade III– IV mucositis. The authors concluded that fludarabinebased regimen including thiotepa or cyclophosphamide along with ATG, followed by a TCD PBSC transplant containing higher numbers of progenitor cells from a different donor, resulted in consistent engraftment. Second allo-HSCT after GF is a medical emergency, and the goal is to proceed with identifying a graft source as early as possible to minimize the time of severe cytopenias. However, careful attention should be given to factors that can be modified to ensure engraftment of the second transplant. Ideally, a perfect HLA-matched donor to whom the patient does not have DSA should be picked for the second allo-HSCT, but if the patient has high DSA, intervention to reduce the DSA titer can be applied before second allo-HSCT. Gladstone et al.37,51 found that plasmapheresis combined with anticytomegalovirus intravenous immunoglobulin, tacrolimus, and mycophenolate mofetil (MMF) starting 1–2 weeks before conditioning, depending on the level of DSA, was associated with a 64.4% mean reduction in DSA levels. Fifteen patients received this treatment, and the 14 patients who achieved DSA reduction to negative or weak levels underwent transplantation and were engrafted. Ciurea et al.39 proposed an alternative desensitization method of plasma exchange, rituximab, and intravenous immunoglobulin, which they found to be only partially effective. However, combining the aforementioned regimen with the infusion of donor HLA antigens via a buffy coat 24 h before stem cell transplant was highly effective. They also reported that clearing of DSA may be unnecessary, with reduction to noncomplement binding levels sufficient to achieve engraftment. 

POOR GRAFT FUNCTION Stem Cell Boost From Original Donor The best course of treatment for PGF is not well defined. Hematopoietic growth factors, namely granulocyte colony-stimulator factor, granulocyte-macrophage colonystimulating factor, erythropoietin, or thrombopoietin receptor agonists have been used but often with less than optimal response.52,53 The administration of additional hematopoietic stem cells after prior conditioning (second allo-HSCT) has had limited success secondary to toxicity of the conditioning regimen and high rates of grade III–IV GVHD.54 An alternative approach is to administer additional donor-derived stem cells,

329

unmanipulated or TCD, without additional conditioning (stem cell boost). The use of unmanipulated donor stem cell boost, however, is associated with a high incidence of acute and chronic GVHD and poor survival rates.55 A boost of TCD stem cells after conventional or TCD allo-HSCT has been more successful mainly related to the low incidence of GVHD.56–58 An important study that demonstrated the benefit of a TCD boost for PGF compared patients treated with either a TCD boost, an unmanipulated stem cell boost, or supportive care alone. Trilineage recovery was more common, and nonrelapse mortality was lower in those receiving donor stem cells after TCD boost (CD34+ selection) compared with the other two groups. In addition, the incidence of GVHD was significantly lower in the TCD group than in the conventional boost arm41,43 (Fig. 23.3). 

Mesenchymal Stromal Cells BM stromal cells such as mesenchymal stromal cells (MSCs) elaborate cytokines that nurture or stimulate the marrow microenvironment by several mechanisms.59–61 MSCs can act as pericytes, wrapping around the endothelial cells of capillaries and venules, and secrete bioactive products that contribute to tissue regeneration.62,63 MSCs could also be selectively immune-suppressive and could affect the production of inhibitory cytokines.64,65 Hence it is possible that administration of MSCs in the setting of incomplete or delayed engraftment can modulate the milieu of the BM microenvironment, through both direct interaction with hematopoietic stem cells and through secretion of cytokines, to improve blood counts after transplantation.66–68 MSCs have inherently low immunogenicity, are poor targets for cytotoxic T cells and NK cells, do not activate allo-reactive T cells in vitro, and do not elicit allogeneic or xenogeneic immunologic response when transplanted. They have uniformly been determined to be safe and tolerable.69 MSCs given at the time of HCT have been shown to improve engraftment, as well as have immunomodulatory effects in murine stem cell transplantation models.70,71 MSCs can be found within multiple sites, including adipose tissue and BM.72,73 The advantage of MSC over stem cell from original donor is that they can be used as “of-the-shelf” product without the need for a second mobilization process from a donor who may or may not be available for a second donation. Also, the lack of alloreactivity associated with MSC is another important advantage. However, further clinical studies are needed to assess the best source of MSC as well as doses and schedule of administration to ensure sustained engraftment. 

SECTION VI  Complications, Infectious Disease, and Special Populations

80% 60%

Acute GvHD ||

40% 20%

15%

0% 0 50 100 150 200 250 300 days from boost CD34 infusion

A

Trilineage recovery

80%

75%

60% 40% 20% 0% 0

274 548 821 1095 days from boost CD34 infusion

B 100% 80%

Survival

cumulative incidence of trilineage recovery

100%

100%

100%

Overall survival 63%

60% 40%

80% Survival

% grade || acute GvHD

330

20% 0% 0 1500 3000 days from boost CD34 infusion

C

60%

Survival Pts with trilineage recovery, n=31

76%

40%

25% 20% Pts without trilineage recovery, n=10 0% 0 1500 3000 4500 days from boost CD34 infusion

D

FIG. 23.3  Outcomes after treatment with a T-cell–depleted boost for poor graft function. (A) Cumulative

incidence of acute GVHD. (B) Trilineage recovery. (C) Overall survival. (D) Comparison of survival based on counts recovery after TCD boost.41 GVHD, Graft-versus-host disease; TCD, T-cell–depleted transplant.

APPROACH In the case of lack of engraftment (primary graft failure) or loss of blood counts after initial engraftment occurred (secondary graft failure), the first and most important question to be addressed is the underlying mechanism, that is, whether there is rejection of the graft or PGF, as the nature of the required intervention is different between the two. When dealing with GR, a second transplant should be arranged as soon as possible particularly if MAC regimen was used for the initial transplant because the likelihood of autologous stem cell recovery is extremely low. If RIC or NMA conditioning regimens were used for the primary transplant, there is a chance of autologous stem cell recovery; however, that may give rise to the primary disease for which the transplant was done. When planning for a second transplant, attention needs to be given to further suppress the host immunity to prevent rejection of the second allo-graft. In the event that other factors have been identified as contributing to the GR, such as high DSA, host-donor mismatched, low cell dose, and so forth, they should be addressed if possible. When dealing with PGF, attention should be given to all potential factors that may be affecting graft function including host nutritional status (i.e., B12/folic

acid deficiencies), presence of enlarged spleen, medications that can be myelosuppressive (i.e., MMF, valacyclovir, and so forth), as well as infections that can be affecting stem cell recovery after allo-HSCT. If all identified reversible causes have been addressed without improvement in blood counts, a T-cell–depleted boost should be considered.

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