Risk Factors Affecting Outcome of Second HLA-Matched Sibling Donor Transplantations for Graft Failure in Severe Acquired Aplastic Anemia

Article Outline

• Abstract
• Introduction
• Patients, Materials, and Methods
  • Patients
  • Study Endpoints
  • Statistical Methods
• Results
  • Hematopoietic Recovery
  • Graft-versus-Host Disease
  • Overall Survival
• Discussion
• Acknowledgements
• References
• Copyright

Abstract 

We examined transplantation outcomes after a second HLA-matched sibling transplantation for primary (16%) or secondary (84%) graft failure in 166 patients with severe acquired aplastic anemia (AA). Two-thirds of these patients has a performance score < 90. In most cases (88%), the same donor was used for both transplants, for both transplantations, and 84% of the second transplantations used bone marrow grafts. We identified 2 prognostic factors: intertransplantation interval (surrogate for primary graft failure and early secondary graft failure) and performance status. Shorter intertransplantation interval (≤ 3 months) and poor performance score (< 90) at second transplantation were associated with high mortality. In patients with a performance score of 90% to 100%, the 8-year probability of overall survival (OS) after second transplantation ≤ 3 and > 3 months from first transplantation was 56% and 76%, respectively. The corresponding probabilities in patients with lower performance scores were 33% and 61%. The predominant cause of failure after second transplantation was nonengraftment (in 72 of 166 patients), most commonly in patients with primary or early secondary graft failure (51 of 72; 71%). Our data indicate that novel approaches, including conditioning regimens with greater immunosuppression, should be explored for these patients.

Key Words: Severe aplastic anemia, Second transplantation, Graft failure

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Introduction 

HLA-matched sibling bone marrow transplantation (BMT) is an effective treatment for acquired severe aplastic anemia (SAA), particularly in children and young adults 1, 2, 3. Despite significant improvements in overall survival (OS) over the last 20 years 2, 4, 5, the rate of graft failure has not changed significantly, remaining approximately 10% 5, 6, 7. Many patients with graft failure undergo a second transplantation with a graft from either the initial donor or a different donor 6, 8, 9. We investigated the factors affecting outcome in 166 patients undergoing a second HLA-matched sibling transplantation for primary or secondary graft failure after an initial HLA-matched sibling transplantation.

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Patients, Materials, and Methods 

Patients 

Data on 166 patients with SAA undergoing a second HLA-matched sibling transplantation between 1986 and 2004 were obtained from the Center for International Blood and Marrow Transplant Research, Medical College of Wisconsin. All of the patients received a BM graft from an HLA-matched sibling for their first transplantation. Six patients who received peripheral blood progenitor cells (PBPCs) for their first transplantation were excluded. The Medical College of Wisconsin's Institutional Review Board approved the study design.

Study Endpoints 

Neutrophil recovery was defined as achieving an absolute neutrophil count (ANC) ≥ 0.5 × 10⁹/L for 3 consecutive days and a platelet count ≥ 20 × 10⁹/L unsupported for 7 days. Acute and chronic graft-versus-host disease (aGVHD, cGVHD) was diagnosed and graded by the transplantation centers using standard criteria [10]. Primary graft failure was defined as failure to achieve an ANC ≥ 0.5 × 10⁹/L for 3 consecutive days; secondary graft failure was defined as a sustained decline in ANC after initial recovery. Death from any cause was considered an event, and all surviving patients were censored at last follow-up.

Statistical Methods 

The probabilities of neutrophil and platelet recovery, aGVHD, and cGVHD were calculated using the cumulative incidence estimator, with death without the event as the competing event [11]. The probabilities of early mortality (day 100) and OS were calculated using the Kaplan-Meier estimator [12]. The 95% confidence interval (CI) was calculated using log-transformation. Regression models for neutrophil and platelet recovery and early mortality were constructed using the pseudovalue method [13], and those for overall mortality were constructed using the Cox regression method [12]. All models were constructed using stepwise forward selection, with a P value ≤ .05 indicating statistical significance. The variables considered in the regression models are listed in Table 1. Only those variables that attained a P value ≤ .05 during model building were retained in the final model. We tested for an effect of transplantation center and found none [14]. All P values are 2-sided, and all analyses were done using SAS version 9.1 (SAS Institute, Cary, NC).

Table 1. Patient, Disease, and Transplant Characteristics

	First Transplantation,	Second Transplantation,	Third Transplantation,
Variable	n (%)	n (%)	n (%)
Number of patients	166	166	23
Age at transplantation, years
≤ 10	64 (39)	56 (34)	11 (48)
11-20	49 (29)	52 (31)	3 (13)
21-30	37 (22)	41 (25)	6 (26)
≥ 31	16 (10)	17 (10)	3 (13)
Male sex	97 (58)	97 (58)	17 (74)
Karnofsky score pretransplantation
< 90	82 (50)	111 (67)	15 (65)
≥ 90	83 (50)	54 (33)	8 (35)
Unknown	1	1	0
Reason for second and third transplantations
Primary graft failure		26 (16)	5 (22)
Secondary graft failure		140 (84)	18 (78)
Intertransplantation interval (first to second transplantation)	NA		NA
≤ 3 months		47 (28)
> 3 months		119 (72)
Conditioning regimen
Cy + ATG	36 (21)	73 (44)	7 (30)
Cy + TBI/TLI/TAI ± other	21 (12)	31 (19)	3 (13)
Cy alone	88 (53)	8 (5)	0
Busulfan + Cy	17 (10)	16 (10)	2 (9)
Other	4 (1)	32 (19)	6 (26)
None∗	0	12 (7)	5 (22)
GVHD prophylaxis
Cyclosporine + methotrexate ± other	134 (80)	104 (63)	0
Cyclopsorine ± other	27 (16)	54 (32)	6 (26)
Methotrexate ± other	3 (2)	1 (1)	13 (57)
Tacrolimus ± other	1 (1)	3 (2)	1 (4)
None		4 (2)	3 (13)
Nucleated cells infused, × 108/kg
< 3.0	42 (26)	39 (25)	8 (38)
≥ 3.0	120 (74)	114 (75)	13 (62)
Unknown	4	13	2
Donor type	N/A
Same related donor as for first transplant		146 (88)	21 (91)
Different related donor		20 (12)	2 (9)
Unrelated donor		0	0
Donor–recipient sex match
Male donor→male recipient	54 (33)	52 (31)	9 (41)
Male donor→female recipient	45 (27)	46 (28)	0
Female donor→male recipient	43 (26)	45 (27)	8 (36)
Female donor→female recipient	24 (14)	23 (14)	5 (23)
Missing	0	0	1
Graft type
BM	166 (100)	140 (84)	16 (70)
PBPCs		26 (16)	7 (30)
Year of transplantation
1986-1989	47 (28)	42 (25)	7 (30)
1990-1993	46 (28)	41 (25)	5 (22)
1994-1997	40 (24)	36 (22)	1 (4)
1998-2002	33 (20)	41 (25)	8 (35)
2003-2004	0	6 (3)	2 (9)
Median follow-up of survivors after second transplantation, months		97 (6-215)	122 (19-188)

NA, indicates not applicable; Cy, cyclophosphamide; TAI, total abdominal irradiation; PBPCs, peripheral blood progenitor cells; BM, bone marrow; GVHD, graft-versus-host disease; TBI, total body irradiation; TLI, total lymphoid irradiation.

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Results 

Table 1 summarizes patient, disease, and transplantation characteristics for the first and second transplantations, as well as for the 23 third transplantations. All patients received BM grafts for the first transplantation; 84% of patients received BM grafts and 16% received PBPCs for the second transplantation. The median time between the first and second transplantations was 7 months (range, 1 to 114 months); 2/3 of the second transplantations occurred within 1 year from the first transplantation.

Hematopoietic Recovery 

The probabilities of neutrophil recovery at day 28 and of platelet recovery at day 60 after second transplantation were 63% (95% CI = 55% to 70%) and 62% (95% CI = 58% to 73%), respectively (Figure 1). Thirty-six patients failed to achieve neutrophil recovery, and 54 patients failed to achieve platelet recovery. In addition, 18 patients experienced graft failure after initial hematopoietic recovery; in 14 of these patients, graft failure occurred within 12 months after second transplantation, and in the remaining 4 patients, graft failure occurred between 13 and 37 months. In multivariate analysis, neutrophil recovery after second transplantation was more likely with PBPCs (odds ratio [OR] = 12.91; 95% CI = 2.65 to 62.83; P = .002) and when the indication for transplantation was secondary graft failure after the first transplantation (OR = 4.39; 95% CI = 1.60 to 12.08; P = .004). Neither performance score (OR = 1.68; 95% CI = 0.84 to 3.37; P = .144) nor conditioning regimen (cyclophosphamide [Cy] with limited field irradiation vs Cy plus antithymocyte globulin [ATG]: OR = 0.56, 95% CI = 0.24 to 1.31, P = .178; other regimens vs Cy plus ATG: OR = 0.99, 95% CI = 0.49 to 2.03, P = .982) was associated with neutrophil recovery.

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• Figure 1 

  Cumulative incidence of neutrophil and platelet recovery after second HLA-matched sibling donor transplantation for graft failure.

Platelet recovery also was more likely after transplantation with PBPCs (OR = 11.25; 95% CI = 2.30 to 54.99; P = .003), when the indication for second transplantation was secondary graft failure (OR = 8.80; 95% CI = 2.63 to 29.43; P < .001), and when the patient's performance score was 90 to 100 (OR = 3.60; 95% CI = 1.47 to 8.81; P = .005). Platelet recovery also was associated with the conditioning regimen for the second transplantation; recovery was less likely in those receiving an irradiation-containing conditioning regimen (OR = 0.22; 95% CI = 0.08 to 0.60; P = .003).

Graft-versus-Host Disease 

The probability of grade II-IV aGVHD by day 100 posttransplantation was 9% (95% CI = 5% to 14%). The 8-year probability of cGVHD was 16% (95% CI = 10% to 22%). The rate of cGVHD was higher after transplantation with PBPCs compared with BM (26% vs 14%), but this difference did not achieve statistical significance (P = .274).

Overall Survival 

With a median follow-up of > 8 years after second transplantation, 97 of 166 patients are alive at the time of this writing. Early (day 100) mortality rates were high (30% [49/166]); primary graft failure (n = 24) was the most frequent cause of death during this period. Fewer deaths (n = 20) occurred beyond 100 days. In multivariate analysis, the performance score at second transplantation and the intertransplantation interval were independent predictors of OS. In patients requiring a second transplantation within 3 months of the first transplantation because of primary or early secondary graft failure, the relative risk (RR) of early mortality was 3.12 (95% CI = 1.47 to 6.62; P = .003), and the RR of overall mortality was 2.15 (95% CI = 1.32 to 3.51; P = .002). In patients with a performance score < 90, the RR of early mortality was 5.81 (95% CI = 2.12 to 16.13; P < .001), and that of overall mortality was 1.88 (95% CI = 1.05 to 3.38; P = .033).

Considering the influence of intertransplantation interval and performance status together, OS was highest in second transplantations done after 3 months from first transplantations and in patients with a performance score of 90 to 100. In patients with such a performance score, the 8-year probability of OS was 56% when the interval between the first and second transplantations was < 3 months and 76% when this interval was > 3 months (Figure 2). The corresponding probabilities in patients with lower performance scores were 33% and 61%. Two transplantation strategies, using a different sibling donor (RR = 1.22; P = .558) and using PBPCs (RR = 0.56; P = .159), were not associated with overall mortality. We found no association between the type of conditioning regimen and overall mortality (Cy with limited-field irradiation vs Cy plus ATG: RR = 1.31, 95% CI = 0.70 to 2.45, P = .394; and other regimens vs Cy plus ATG: RR = 1.00, 95% CI = 0.58 to 1.72, P = .993). Twenty-three patients underwent a third transplantation for secondary graft failure after the second transplantation (Table 1). Of these 23 patients, 15 achieved sustained hematopoietic recovery and 11 were alive at last follow-up. Table 2 presents the causes of death for the entire cohort; as shown, the 2 most common causes were graft failure and infection.

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• Figure 2 

  Overall survival after second HLA-matched sibling donor transplantation for graft failure in SAA by time between first to second transplantation and Karnofsky performance score. Eight-year probability of overall survival in patients with a performance score of 90 to 100 and an intertransplantation interval > 3 months (…… ; 76% [95% CI = 62% to 88%]); in patients with a performance score < 90 and an intertransplantation interval > 3 months (– – – –; 61% [95% CI = 50% to 72%]); in patients with a performance score of 90 to 100 and an intertransplantation interval < 3 months (- - - - -; 56% [95% CI = 24% to 85&]); and in patients with a performance score < 90 and an intertransplantation interval < 3 months (———; 33% [95% CI = 19% to 49%]).

Table 2. Causes of Death in 69 Patients Evaluated

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Discussion 

In this study, we identified 2 factors associated with survival after second HLA-matched sibling transplantation for SAA: intertransplantation interval of > 3 months and good performance score (90 to 100) at second transplantation. Intertransplantation interval serves as a surrogate for the type and rapidity of graft failure, allowing cases of primary graft failure or early secondary graft failure to be distinguished from cases of late secondary graft failure. When the cohort was stratified by intertransplantation interval and performance score, 3 prognostic groups emerged. Patients with an intertransplantation interval > 3 months and a good performance score did well in the long term, with an estimated 8-year survival of 76%, whereas those with an intertransplantation interval < 3 months and a performance score < 90 fared poorly, with an estimated 8-year survival of 33%. Patients with a long intertransplantation interval, but a suboptimal performance score or a good performance score, but a short intertransplantation interval had an intermediate outcome (estimated 8-year survival rate of 61% and 56%, respectively). Our observations are limited to patients who failed their first transplantation and underwent a second transplantation. Only 1/3 of patients with primary or secondary graft failure after first transplantation for SAA undergo a second transplantation (Unpublished data, Center for International Blood and Marrow Transplant Research, January 2009). The decision to offer a second transplantation is at the discretion of the treating physician, and the rationale for not offering a second transplantation is not collected by this registry. This represents a limitation when analyzing data collected by an observational database.

Our finding of an association between a longer intertransplantation interval and increased survival substantiates the findings of 3 previous studies 8, 9, 15. Two of those studies demonstrated an association between a longer intertransplantation interval and survival, and the other demonstrated an association between secondary graft failure and survival. (Most of the patients in our analysis with secondary graft failure also had a long intertransplantation interval.) That a short intertransplantation interval is disadvantageous is not surprising; performing a second transplantation too soon after the first allows insufficient time to recover from the toxicity or the myelosuppressive effects of conditioning, increasing the risk of death from infection or organ injury. Moreover, the rapidity of graft failure may reflect the potency of the barrier to sustained engraftment with the conditioning regimens used during the study era. Most of our patients received Cy with or without ATG and limited-field irradiation. Although this regimen is effective for first transplantations, regimens with greater immunosuppressive potency may be required for sustained engraftment in patients requiring a second transplantation.

The type of GVHD prophylaxis had no noticeable effect on outcome. This finding runs counter to results reported by Stucki et al. [9]. In that study, which examined transplantations between 1970 and 1997, higher survival was associated with the use of a cyclosporine and methotrexate (CsA/MTX) combination prophylaxis regimen as opposed to an MTX alone regimen. The lack of effect of GVHD prophylaxis in our study can best be explained by the fact that virtually all of the patients who underwent transplantation in this more recent period received calcineurin inhibitor–based GVHD prophylaxis.

We found no relationships between the various conditioning regimens used and survival. The intensity of the regimens used was fairly similar, which may explain our inability to identify regimens that may have enhanced hematopoietic recovery, particularly in those with primary or early secondary graft failure. The observed negative association between irradiation-based conditioning regimens and platelet recovery is difficult to account for, because the use of irradiation has been associated with sustained engraftment in previous studies [6].

Using a different sibling donor for the second transplantation conferred no detectable advantage in our analysis. Similarly, even though the use of PBPC grafts was associated with improved myeloid recovery (both neutrophils and platelets), it had no measurable effect on survival. A recent study from the Center for International Blood and Marrow Transplant Research comparing PBPC and BM grafts in first transplantations in patients with SAA found a higher rate of cGVHD and lower survival after PBPC transplantations in younger patients [16]. In the absence of a graft-versus-tumor effect for SAA, the burden of morbidity and late mortality associated with cGVHD must be weighed against any potential benefit derived from faster hematopoietic recovery 17, 18.

New approaches are needed for patients undergoing a second transplantation for SAA, particularly those with primary or early secondary graft failure and a poor performance score, in whom the prognosis is dismal. Efforts should focus on preventing graft failure after the first transplantation by optimizing the conditioning regimen (Cy and ATG) and GVHD prophylaxis with a calcinuerin inhibitor and a short course of MTX. Transplantation of PBPCs results in faster hematopoietic recovery but does not translate into a survival advantage. Approximately 45% of our patients received CsA and ATG, and the rest received various other conditioning regimens. Given our relatively small study population (166 patients), we were unable to identify an optimal regimen that may ensure sustained hematopoietic recovery. Nevertheless, Cy and ATG, the most frequently used regimen, was successful in several patients. Although conditioning regimens with greater immunosuppression or myeloablation merit consideration in patients with early graft failure, the risks and benefits of such regimens must be carefully weighed.

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Acknowledgements 

Financial disclosure: This work was supported by Public Health Service Grant U24-CA76518-08 from the National Cancer Institute, the National Heart, Lung and Blood Institute, and the National Institute of Allergy and Infectious Diseases; Health Resources and Services Administration Grant HHSH234200637015C; Office of Naval Research Grants N00014-06-1-0704 and N00014-08-1-0058; and grants from AABB, Aetna, American Society for Blood and Marrow Transplantation, Amgen Inc, Association of Medical Microbiology and Infectious Disease Canada, Astellas Pharma US Inc, Baxter International Inc, Bayer HealthCare Pharmaceuticals, BloodCenter of Wisconsin, Blue Cross and Blue Shield Association, Bone Marrow Foundation, Canadian Blood and Marrow Transplant Group, Celgene Corp, CellGenix GmbH, Centers for Disease Control and Prevention, ClinImmune Labs, CTI Clinical Trial and Consulting Services, Cubist Pharmaceuticals, Cylex Inc, CytoTherm, DOR BioPharma Inc, Dynal Biotech (an Invitrogen company), Enzon Pharmaceuticals Inc, European Group for Blood and Marrow Transplantation, Gambro BCT Inc, Gamida Cell Ltd, Genzyme Corp, Histogenetics Inc, HKS Medical Information Systems, Hospira Inc, Infectious Diseases Society of America, Kiadis Pharma, Kirin Brewery Co Ltd, Merck & Company, The Medical College of Wisconsin; MGI Pharma Inc, Michigan Community Blood Centers, Millennium Pharmaceuticals Inc, Miller Pharmacal Group, Milliman USA Inc, Miltenyi Biotec Inc, National Marrow Donor Program, Nature Publishing Group, New York Blood Center, Novartis Oncology, Oncology Nursing Society, Osiris Therapeutics Inc, Otsuka Pharmaceutical Development & Commercialization Inc, Pall Life Sciences, PDL BioPharma Inc, Pfizer Inc, Pharmion Corp, Saladax Biomedical Inc, Schering Plough Corp, Society for Healthcare Epidemiology of America, StemCyte Inc, StemSoft Software Inc, Sysmex, Teva Pharmaceutical Industries, The Marrow Foundation, THERAKOS Inc, Vidacare Corp, Vion Pharmaceuticals Inc, ViraCor Laboratories, ViroPharma Inc, and Wellpoint Inc. The views expressed in this article do not reflect the official policy or position of the National Institutes of Health, Department of the Navy, Department of Defense, or any other agency of the US Government.

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