Unrelated donor stem cell transplantation in acquired severe aplastic anemia: a systematic review

Outcome of first or second transplantation using unrelated umbilical cord blood without ATG conditioning regimen for pediatric bone marrow failure disorders

BACKGROUND

Unrelated umbilical cord blood transplantation (UCBT) for bone marrow failure (BMF) disorders using conditioning regimens without Anti-Thymocyte Globulin (ATG) has been used as an alternative transplantation for emerging patients without matched-sibling donors. Experience with this transplant modality in children is limited, especially as a secondary treatment for transplant failure patients.

PROCEDURE

We retrospectively reviewed 17 consecutive bone marrow failure patients who underwent unrelated umbilical cord blood transplantation in our center and received conditioning regimens of Total Body Irradiation (TBI) or Busulfan (BU) + Fludarabine (FLU) + Cyclophosphamide (CY).

RESULTS

Among the 17 BMF patients, 15 patients were treated with first cord blood transplantation and another 2 with secondary cord blood transplantation because of graft failure after first haploidentical stem cell transplantation at days +38 and +82. All patients engrafted with a median donor cell chimerism of 50 % at days +7 (range, 16 %-99.95 %) and finally rose to 100 % at days +30. Median time to neutrophil engraftment was 19 days (range, 12-30) and time to platelet engraftment was 32 days (range, 18-61). Pre-engraftment syndrome (PES) was found in 16 patients (94.11 %, 16/17). Cumulative incidence of grades II to IV acute GVHD was 58.8 % (95 % CI: 32.7-84.9 %), and 17.6 % (95 % CI: 2.6-37.9 %) of patients developed chronic GVHD. The 3-year overall survival (OS) and failure-free survival (FFS) rates were 92.86 ± 6.88 %.

CONCLUSION

UCBT is an effective alternative treatment for bone marrow failure pediatric patients. TBI/BU + FLU + CY regimen ensure a high engraftment rate for unrelated umbilical cord blood transplantation, which overcomes the difficulty of graft failure. Secondary salvage use of cord blood transplantation may still be useful for patients who have failed after other transplantation.

Studying the pathogenicity of 26 variants characterized in the first molecular analyses of Egyptian aplastic anemia patients

BACKGROUND

Aplastic anemia (AA) is a bone marrow disorder characterized by peripheral pancytopenia and marrow hypoplasia which can lead to life-threatening complications. Our objective was to study the telomerase genes (TERT and TERC) variants, explore their relationship to telomere shortening and TERT gene expression, and to identify variants in the MPL gene within Egyptian AA patients.

METHODS

Forty AA patients and 40 sex- and age-matched healthy individuals as the control group were studied through sequencing of TERT, TERC, and MPL genes. Quantitative real-time PCR (qRT-PCR) was used for measuring TERT gene expression. Telomere length (TL) was measured using the Quantitative Fluorescence In Situ Hybridization (Q-FISH) technique. In silico analysis was performed for the prediction of the pathogenicity of resultant variants.

RESULTS

Sequencing of MPL, TERT, and TERC genes identified 26 variants. Eleven variants were identified in the MPL gene. Three of them are pathogenic: two missense [c.305 G>A, c.1589 C>T] and one splice site [g.9130T>G]. TERT gene sequencing showed thirteen variants, among them, four novel [c.484G>A, c.499G>A, c.512G>A, c.3164C>G] and two previously reported [c.835G>A, c.2031C>T] were predicted to be pathogenic. Two variants were characterized within the TERC gene; n.514A>G and n.463 C>T. TERT gene expression was downregulated in 70% of studied patients and the Q-FISH technique detected telomere shortening in 82.5% of patients.

CONCLUSIONS

Twenty-six pathogenic and benign variants within the TERC, TERT, and MPL genes were identified among the studied AA patients that were in several cases associated with shortened telomeres and/or lower TERT gene expression. Genotype/phenotype correlation in AA patients is of great importance in explaining the disease severity and guiding therapeutic decisions.

Allogeneic hematopoietic stem cell transplantation in aplastic anemia: current indications and transplant strategies

Treatment options for newly diagnosed aplastic anemia (AA) patient includes upfront allogeneic hematopoietic stem cell transplant (HSCT) or immunosuppressive therapy (IST). With recent advances in supportive care, conditioning regimens and post-transplant immunosuppression the overall survival for HSCT approaches 70-90%. Transplant eligibility needs to be assessed considering age, comorbidities, donor availability and probability of response to immunosuppressive therapy (IST). Upfront HSCT should be offered to children and young adults with matched related donor (MRD). Upfront HSCT may also be offered to children and young adults with rapidly available matched unrelated donor (MUD) who require urgent HSCT. Bone marrow (BM) graft source and cyclosporine (CsA) plus methotrexate (MTX) as graft versus host disease (GVHD) prophylaxis are preferable when using anti-thymocyte globulin (ATG) based conditioning regimens. Alemtuzumab is an acceptable alternative to ATG and is used with CsA alone and with either BM or peripheral blood stem cells (PBSC). Cyclophosphamide (CY) plus ATG conditioning is preferable for patients receiving MRD transplant, while Fludarabine (Flu) based conditioning is reserved for older adults, those with risk factors of graft failure and those receiving MUD HSCT. For haploidentical transplant, use of low dose radiotherapy and post-transplant cyclophosphamide has resulted in a marked reduction in graft failure and GVHD.

Haploidentical hematopoietic stem cell transplantation in aplastic anemia: a systematic review and meta-analysis of clinical outcome on behalf of the severe aplastic anemia working party of the European group for blood and marrow transplantation (SAAWP of EBMT)

Aplastic anemia (AA) is a serious hematological disorder, which is solely cured by hematopoietic stem cell transplantation (HSCT). Haploidentical HSCT is an emerging modality with encouraging outcomes in several blood conditions. The present study aims to comprehensively assess the feasibility and safety of haploidentical HSCT in patients with severe and very severe AA. It is a systematic review and meta-analysis of studies related to haploidentical stem cell transplantation in idiopathic AA investigating rates of successful engraftment, acute graft-versus-host disease (aGvHD), chronic GvHD (cGvHD), transplant-related mortality (TRM), and posttransplantation viral infections (including cytomegalovirus [CMV]) in patients with AA. The effects of reduced-intensity conditioning (RIC) and nonmyeloablative conditioning (NMA), as well as various GvHD prophylaxis regimens on these outcomes were evaluated. In total 15 studies were identified, (577 patients, 58.9% males), successful engraftment was observed in 97.3% of patients (95% CI, 95.9-98.7) while grades II-IV aGvHD and cGvHD were reported in 26.6% and 25.0%, respectively. The pooled incidence of TRM was 6.7% per year (95% CI, 4.0-9.4). RIC regimens were associated with higher proportions of successful engraftment (97.7% vs 91.7%, P = 0.03) and aGvHD (29.5% vs 18.7%, P = 0.008) when compared with NMA regimens with no differences in cGvHD or mortality incidence. When compared with methotrexate-containing regimens and other regimens, posttransplant cyclophosphamide-containing regimens reduced the rates of aGvHD (28.6%, 27.8%, and 12.8%, respectively, P = 0.02), CMV viremia (55.7%, 38.6%, and 10.4%, respectively, P < 0.001), and CMV disease in initially viremic patients (2.1%, 33.0%, and 0%, respectively, P < 0.001). We have concluded that Haploidentical HSCT was associated with promising outcomes in terms of successful engraftment and reduced complications. Future prospective trials are needed to identify the preferred conditioning regimen, GvHD prophylaxis, and graft source in the setting of haploidentical transplant for AA.

Allogeneic Bone Marrow Transplants for Pediatric Severe Aplastic Anemia: Real-world Data comparing Matched Related and Unrelated Donors in a Developing Country. Retrospective study on behalf of the Pediatric Hematopoietic Stem Cell Transplant Working Group of the Brazilian Bone Marrow Transplantation Society (SBTMO) and the Brazil-Seattle Consortium (Gedeco)

In this study, we report on major MRD or URD BMT outcomes in pediatric patients with SAA in Brazil. This was a retrospective study, which included 106 patients ≤18 years old who received a first BMT for SAA. All patients received bone marrow as graft source from an MRD (n = 69) or a URD (n = 37). Conditioning regimen was non-myeloablative in 73.6% of cases, and GVHD prophylaxis comprised a calcineurin inhibitor plus methotrexate in 89.6% of patients. After a median follow-up of 4.5 years after BMT, 81 patients are alive, with a 4-year OS of 77% and no statistically significant difference between the MRD and URD groups (82% vs. 69%, respectively; P = .08). Grade III-IV aGVHD at 6 months and cGVHD at 2 years were observed in 8% and 14% of cases, respectively, and were not statistically different between the groups. Twenty-five (23%) patients died at a median of 2.9 months after BMT. Our study showed that 4-year OS after BMT was not statistically different between MRD and URD recipients. This study shows that the outcomes of pediatric patients transplanted for SAA with a URD in Brazil are approaching those of MRD transplants. In contrast, OS after MRD BMT was lower than we would expect based on previous reports. The wide range of preparatory regimens used by the study centers highlights the need for standardized protocols for these children. Our findings provide a benchmark for future studies focused on improving BMT outcomes in this setting in Brazil.

Successful engraftment after infusion of multiple low doses of CD34+ cells from a poorly matched sibling donor in a patient with severe aplastic anemia

The dose of CD34+ cells is known to influence the outcome of allogeneic peripheral blood stem cell (PBSC) and/or T-cell-depleted transplantation. A previous study proposed that 2×10⁶ CD34+ cells/kg is the ideal minimum dose for allogeneic transplantation, although lower doses did not preclude successful therapy. In the case we present here, CD34+ cells were collected from a matched sibling donor on the day of allogeneic hematopoietic stem cell transplantation; however, the number of cells was not sufficient for transplantation. Consequently, PBSCs were collected three additional times and were infused along with cord blood cells from the donor that were cryopreserved at birth. The cumulative dose of total nuclear cells and CD34+ cells was 15.9×10⁸ cells/kg and 0.95×10⁶ cells/kg, respectively. White blood cells from this patient were engrafted on day 12. In summary, we report successful engraftment after infusion of multiple low doses of CD34+ cells in a patient with severe aplastic anemia.

Efficacy and Safety of Eltrombopag for Aplastic Anemia: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVES

Eltrombopag seems to be effective in treating patients with aplastic anemia in several clinical trials. This paper aims to perform the first meta-analysis analyzing the efficacy and safety of eltrombopag for aplastic anemia.

METHODS

Literatures were retrieved from PubMed, EMBASE, OVID, Web of Science, Cochrane, Wanfang, http://clinicaltrials.gov and World Health Organization International Clinical Trials Registry Platform search portal from establishment to July 2018. Using Stata statistical software version 12.0, subgroup analyses and sensitivity analyses were conducted.

RESULTS

The overall hematologic response rate is 88% (95% CI 83-94%) for patients treated with eltrombopag plus immunosuppressive therapy, and 47% (95% CI 38-56%) for patients with refractory aplastic anemia using eltrombopag alone. Karyotype abnormality rates include an overall rate of 10% (95% CI 7-14%), a subtotal rate of 8% (95% CI 3-13%) for patients who are treated with eltrombopag plus immunosuppressive therapy without using antithymocyte globulin before, and a subtotal rate of 17% (95% CI 10-24%) for patients with refractory aplastic anemia treated with eltrombopag alone.

CONCLUSIONS

With different treatments and in different conditions eltrombopag showed a distinctive effect for aplastic anemia. However, clone evolution and adverse events were associated with treatment.

Outcome of Second Transplantation Using Umbilical Cord Blood for Graft Failure after Allogeneic Hematopoietic Stem Cell Transplantation for Aplastic Anemia

Graft failure (GF) is the most critical life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT) for aplastic anemia, for which a second transplantation is the only effective treatment. Optimal procedures have not been established for the second transplantation in this setting, however. Here we retrospectively analyzed the outcomes of 22 patients with aplastic anemia, age ≥16 years, who underwent umbilical cord blood transplantation for GF after the first HSCT using the registry database of the Japan Society for Hematopoietic Cell Transplantation. The median age of patients was 36 years (range, 16 to 72 years), and the median time from the first to the second transplant was 77 days (range, 29 to 1061 days). The cumulative incidence of neutrophil engraftment at day 60 post-transplantation was 45.5% (95% confidence interval [CI], 23.6% to 65.0%). With a median follow-up of 50 months, the 4-year overall survival (OS) was 38.5% (95% CI, 18.4% to 58.5%). Mycofenolate mofetil-based graft-versus-host disease prophylaxis demonstrated greater neutrophil recovery than prophylaxis with calcineurin inhibitor alone or methotrexate-based prophylaxis (66.7% versus 37.5%; P = .04). The use of such conditioning regimens as fludarabine + melphalan or cyclophosphamide + low-dose total body irradiation was associated with better engraftment (58.3% versus 30%; P = .05) and better 4-year OS (55.6% versus 20%; P = .05) than other regimens. Although further investigation is needed, umbilical cord blood could be an effective and promising option for stem cell source for urgent second transplantation in patients with aplastic anemia who develop GF after the first HSCT.

Allogeneic hematopoietic stem cell transplantation for nonmalignant hematologic disorders using chemotherapy-only cytoreductive regimens and T-cell-depleted grafts from human leukocyte antigen-matched or -mismatched donors

Nonmalignant hematologic disorders (NMHD) of childhood comprise a variety of disorders, including acquired severe aplastic anemia and inherited marrow failure syndromes. Patients with high-risk NMHD without matched related donors fare poorly with allogeneic hematopoietic alternative donor stem cell transplantation (allo-HSCT) and are at high risk for developing graft-versus-host disease following unmodified grafts. The authors retrospectively analyzed data on 18 patients affected by NMHD, lacking a human leukocyte antigen (HLA)-identical sibling donor, who underwent an alternative donor allo-HSCT at their institution between April 2005 and May 2013. Fifty percent of the patients had received prior immunosuppressive therapy, 72% had a history of infections, and 56% were transfusion dependent at the time of transplant. Cytoreduction included a combination of 3 of 5 agents: fludarabine, melphalan, thiotepa, busulfan, and cyclophosphamide. Grafts were T-cell depleted. All evaluable patients engrafted. Five died of transplant complications. The cumulative incidence of graft-versus-host disease was 6%. No patient had recurrence of disease. Five-year overall survival was 77%. Age at transplant <6 years was strongly associated with better survival. Based on these results, transplant with chemotherapy-only cytoreductive regimens and T-cell-depleted stem cell transplants could be recommended for patients with high-risk NMHD, especially at a younger age.

Cyclophosphamide conditioning in patients with severe aplastic anaemia given unrelated marrow transplantation: a phase 1-2 dose de-escalation study

BACKGROUND

The optimum preparative regimen for unrelated donor marrow transplantation in patients with severe aplastic anaemia remains to be established. We investigated whether the combination of fludarabine, anti-thymocyte globulin, and total body irradiation (TBI) would enable reduction of the cyclophosphamide dose to less than 200 mg/kg while maintaining engraftment and having a survival similar to or better than that with standard regimens using a cyclophosphamide dose of 200 mg/kg (known to be associated with significant organ toxicity) for unrelated donor transplantation for severe aplastic anaemia. We have previously shown that cyclophosphamide at 150 mg/kg resulted in excess toxicity and its omission (0 mg/kg) resulted in unacceptable graft failure (three of three patients had secondary graft failure). Here we report results for the 50 mg/kg and 100 mg/kg cohorts.

METHODS

In a multicentre phase 1-2 study, patients (aged ≤65 years) with severe aplastic anaemia, adequate organ function, and an unrelated adult marrow donor HLA matched at the allele level for HLA A, B, C, and DRB1 or mismatched at a single HLA locus received bone marrow grafts from unrelated donors. All patients received anti-thymocyte globulin (rabbit derived 3 mg/kg per day, intravenously, on days -4 to -2, or equine derived 30 mg/kg per day, intravenously, on days -4 to -2), fludarabine (30 mg/m(2) per day, intravenously, on days -5 to -2), and TBI (2 Gy). Cyclophosphamide dosing started at 150 mg/kg and was de-escalated in steps of 50 mg/kg (to 100 mg/kg, 50 mg/kg, and 0 mg/kg). The primary endpoint was the selection of the optimum cyclophosphamide dose based on assessments of graft failure (primary or secondary), toxicity, and early death during 100 days of follow-up after the transplant; this is the planned final analysis for the primary endpoint. This trial is registered with ClinicalTrials.gov, number NCT00326417.

FINDINGS

96 patients had bone marrow transplant. At day 100, 35 (92%) of 38 patients were engrafted and alive in the cyclophosphamide 50 mg/kg cohort and 35 (85%) of 41 in the 100 mg/kg cohort. Cyclophosphamide 50 mg/kg and 100 mg/kg resulted in posterior means for fatality without graft failure of 0·7% (credible interval 0-3·3) and 1·4% (0-4·9), respectively. Three patients (8%) had graft failure with cyclophosphamide 50 mg/kg and six (15%) with cyclophosphamide 100 mg/kg. Four (11%) patients had major regimen-related toxicity with cyclophosphamide 50 mg/kg and nine (22%) with cyclophosphamide 100 mg/kg. The most common organ toxicity was pulmonary (grade 3 or 4 dyspnoea or hypoxia including mechanical ventilation), and occurred in three (8%) and four (10%) patients given cyclophosphamide 50 mg/kg and 100 mg/kg, respectively.

INTERPRETATION

Cyclophosphamide at 50 mg/kg and 100 mg/kg with TBI 2 Gy, fludarabine, and anti-thymocyte globulin results in effective conditioning and few early deaths after unrelated donor transplantation for severe aplastic anaemia. These doses of cyclophosphamide provide a framework for further regimen optimisation strategies.

FUNDING

US National Heart, Lung, and Blood Institute and National Cancer Institute.

Second allogeneic stem cell transplant for aplastic anaemia: a retrospective study by the Severe Aplastic Anaemia Working Party of the European Society for Blood and Marrow Transplantation

We analysed the outcome of a second allogeneic haematopoietic stem cell transplant (alloHSCT) in 162 patients reported to the European Society for Blood and Marrow Transplantation between 1998 and 2009. Donor origin was a sibling in 110 and an unrelated donor in 52 transplants, respectively. The stem cell source was bone marrow in 31% and peripheral blood in 69% of transplants. The same donor as for the first alloHSCT was used in 81% of transplants whereas a change in the choice of stem cell source was reported in 56% of patients, mainly from bone marrow to peripheral blood. Neutrophil and platelet engraftment occurred in 85% and 72% of patients, after a median time of 15 and 17 days, respectively. Grade II-IV acute graft-versus-host disease (GVHD) and chronic GVHD occurred in 21% and 37% of patients, respectively. Graft failure (GF) occurred in 42 patients (26%). After a median follow-up of 3·5 years, the 5-year overall survival (OS) was 60·7%. In multivariate analysis, the only factor significantly associated with a better outcome was a Karnofsky/Lansky score ≥80 (higher OS). We conclude that a second alloHSCT is feasible rescue option for GF in SAA, with a successful outcome in 60% of cases.

Matched related donor hematopoietic stem cell transplantation results in a long-term follow-up of a pediatric acquired severe aplastic anemia subset: A stem cell source perspective

HSCT has substantially improved pediatric acquired SAA patients' outcomes. Retrospectively, we attempted to assess the outcome of MRD HSCT in 65 pediatric patients referred to a single center from 1992 to 2012. We were particularly interested to find out whether source of SC (PB, n = 40 and BM, n = 25) significantly impacts EFS and GVHD incidence. With a median follow-up of 45 months, total EFS was 87.7%; EFS for PB and BM groups was 87.5% and 88%, respectively. Acute GVHD (grades 3-4) occurred in 13 patients (PB, n = 10 [25%] and BM, n = 3 [12%]), acute GVHD (grades 2-4) occurred in 24 (PB, n = 16 [40%] and BM, n = 8 [32%]). Extensive chronic GVHD occurred in five patients (PB, n = 3 [7.5%] and BM, n = 2 [8%]). Cox regression revealed that elapsed time of <10 months between diagnosis and HSCT is associated with improved survival (hazard ratio, 95% CI = 1.204, 1.010-1.434, p = 0.038). SC source did not significantly affect EFS, incidence of acute GVHD (grades 3-4), or extensive chronic GVHD (p = 0.938, 0.121, and 0.487, respectively). Based on our findings, pediatric acquired SAA patients are benefitted most if MRD-HSCT is carried out early in disease process and SC source does not affect outcome of MRD-HSCT in these patients.

Allogeneic hematopoietic stem cell transplantation as the first-line treatment option in a patient with severe aplastic anemia without a matched related donor: A case report

The outcomes of matched unrelated donor (MUD) hematopoietic stem cell transplantation (HSCT) and immunosuppressive therapy (IST) in patients with severe aplastic anemia (SAA) remain controversial. The clinical outcome in patients that undergo transplantation following failed IST is typically poorer when compared with patients that initially underwent transplantation. Clinical treatment algorithms have been proposed to determine the management of such patients, and account for individual conditions, personal preferences and prognostic risk factors. The present study reports the promising outcome of a 22-year-old patient exhibiting SAA. The patient underwent peripheral blood stem cell transplantation (PBSCT) from an MUD using a fludarabine-based conditioning regimen and low-dose total body irradiation as an alternative method to first-line IST. The patient achieved rapid bone marrow reconstitution and has been in complete remission for 32 months. The aim of the fludarabine-based conditioning regimen with PBSCT was to improve the patient’s therapeutic outcome and provide a convenient treatment strategy. Furthermore, this regimen extends the application of HSCT to patients who are older or those that are without a matched related donor.

New therapeutic approaches for protecting hematopoietic stem cells in aplastic anemia

Aplastic anemia (AA) is an immune-mediated and life-threatening form of acquired bone marrow failure (BMF), characterized by development and expansion of self-reactive T cells. These T cells cause continuous destruction of hematopoietic stem cells (HSCs), progenitors, and mature blood cells, leading to severe and if left untreated fatal marrow hypoplasia and pancytopenia. Standard treatment options for patients with AA include: (1) immunosuppressive therapy (IST) with anti-thymocyte globulin and cyclosporine A which targets self-reactive T cells, or (2) matched sibling or unrelated BM transplant (BMT). The IST treatment is often not effective due to poor response to therapy or disease relapse after IST. Also, BMT is not an option for many patients due to their age, comorbidities, and the lack of histocompatible donor. This necessitates development and testing of novel approaches to reduce severity of AA and to efficiently treat patients with refractory and relapsed AA. Immune-mediated AA was reproduced in animals, including mouse lymphocyte infusion models, which are used to study further etiology and pathophysiology of AA and test new drugs and approaches in treating and managing AA. In these mouse models the immune correlates and pathologic features of AA are strikingly similar to features of severe human AA. In this article we (a) briefly review standard and developing approaches for treating AA and (b) describe development and testing of novel treatment approach with a potential to safely reduce BM hypoplasia and significantly decrease the loss of HSCs in mouse lymphocyte infusion model of AA.

Effect of race on outcomes after allogeneic hematopoietic cell transplantation for severe aplastic anemia

We compared outcomes after hematopoietic cell transplantation in patients of African American (n = 84) and Caucasian (n = 215) descent with severe aplastic anemia. African Americans and Caucasians were matched for age, donor-recipient human leukocyte antigen match, graft type, and transplantation year. The median follow-up of surviving patients was 5 years. In multivariate analysis, overall mortality risks were higher for African Americans compared to Caucasians (relative risk 1.73, P = 0.01). The 5-year probabilities of overall survival adjusted for interval from diagnosis to transplantation, and performance score was 58% for African Americans and 73% for Caucasians. The day-100 cumulative incidence of grade III-IV, but not grade II-IV acute graft-versus-host disease (GVHD), was higher in African Americans compared to Caucasians (29% vs. 13%, P = 0.006). Although the 5-year cumulative incidence of chronic GVHD was not significantly different between the racial groups, African Americans were more likely to have extensive chronic GVHD compared to Caucasians (72% vs. 49%, P = 0.06). Survival differences between Caucasians and African Americans can be attributed to multiple factors. Our data suggest that some of the observed survival differences between Caucasians and African Americans may be explained by higher rates of acute GVHD and severity of chronic GVHD.

Outcome of patients activating an unrelated donor search for severe acquired aplastic anemia

Patients with severe aplastic anemia (SAA) without a sibling donor receive immunosuppressive treatment (IST) with anti-thymocyte globulin (ATG). In the case of no response to IST, a voluntary unrelated donor (VUD) search is usually started. This study analyzes the outcome of ATG-refractory SAA patients activating a VUD search. Of 179 patients, 68 had at least one HLA-A, -B, and -DR matched donor identified and underwent HSCT while 50 also with a donor were not transplanted because of early death (8), late response to IST (34), transplant refusal (1), or other (7). Conversely, 61 had no matched donor, 13 of those ultimately received a mismatched HSCT. All but one received marrow stem cells. Among patients aged <17 years, those with at least one matched donor had a significant higher 4-year survival as compared to others (79% ± 6% versus 53% ± 10%, P = 0.01). There was also a survival advantage independent of recipient age when the donor search was initiated in the recent 2000-2005 study-period (74% ± 6% versus 47% ± 10%, P < 0.05). In multivariate analysis, the identification of a matched VUD tended to impact favourably on survival in patients with a recent donor search (P = 0.07). This study provides evidence for the use of unrelated donor HSCT in children and adults with IST-refractory SAA.

Aplastic anemia: therapeutic updates in immunosuppression and transplantation

Advances in hematopoietic stem cell transplantation (HSCT) and immunosuppressive therapy (IST) have improved survival in severe aplastic anemia (SAA) from 10%-20% in the 1960s to 80%-90% today. A matched sibling HSCT is the treatment of choice in younger patients, whereas IST is often used in older patients or in those who lack a histocompatible sibling. Graft rejection, GVHD, and poor immune reconstitution (with associated infectious complications) limit the success of HSCT, whereas lack of response, relapse, and clonal evolution limit the success of IST. The historically high rate of graft rejection in SAA is now less problematic in the matched setting, but with greater rates observed with unrelated and umbilical cord donors. The correlation of increasing age with the risk of GVHD and the significant morbidity and mortality of this transplantation complication continue to affect the decision to pursue HSCT versus IST as initial therapy in adults with SAA. Outcomes with matched unrelated donor HSCT have improved, likely due to better donor selection, supportive care, and improved transplantation protocols. Results with mismatched unrelated donor and umbilical HSCT are not as favorable, with higher rates of graft rejection, GVHD, and infectious complications. Investigation of several upfront alternative IST protocols has not improved outcomes beyond horse antithymocyte globulin and cyclosporine. More recently, the role of alemtuzumab in SAA has been better defined and an oral thrombomimetic, eltrombopag, is showing promising activity in refractory cases. The most recent advances in HSCT and IST in SAA are discussed in this review.

Fludarabine-based conditioning for marrow transplantation from unrelated donors in severe aplastic anemia: early results of a cyclophosphamide dose deescalation study show life-threatening adverse events at predefined cyclophosphamide dose levels

Excessive adverse events were encountered in a Phase I/II study of cyclophosphamide (CY) dose deescalation in a fludarabine-based conditioning regimen for bone marrow transplantation from unrelated donors in patients with severe aplastic anemia. All patients received fixed doses of antithymocyte globulin, fludarabine, and low-dose total body irradiation. The starting CY dose was 150 mg/kg, with deescalation to 100 mg/kg, 50 mg/kg, or 0 mg/kg. CY dose level 0 mg/kg was closed due to graft failure in 3 of 3 patients. CY dose level 150 mg/kg was closed due to excessive organ toxicity (n = 6) or viral pneumonia (n = 1), resulting in the death of 7 of 14 patients. CY dose levels 50 and 100 mg/kg remain open. Thus, CY at doses of 150 mg/kg in combination with total body irradiation (2 Gy), fludarabine (120 mg/m(2)), and antithymocyte globulin was associated with excessive organ toxicity.

How I treat acquired aplastic anemia

Survival in severe aplastic anemia (SAA) has markedly improved in the past 4 decades because of advances in hematopoietic stem cell transplantation, immunosuppressive biologics and drugs, and supportive care. However, management of SAA patients remains challenging, both acutely in addressing the immediate consequences of pancytopenia and in the long term because of the disease's natural history and the consequences of therapy. Recent insights into pathophysiology have practical implications. We review key aspects of differential diagnosis, considerations in the choice of first- and second-line therapies, and the management of patients after immunosuppression, based on both a critical review of the recent literature and our large personal and research protocol experience of bone marrow failure in the Hematology Branch of the National Heart, Lung, and Blood Institute.

Clinical management of aplastic anemia

Acquired aplastic anemia is a potentially fatal bone marrow failure disorder that is characterized by pancytopenia and a hypocellular bone marrow. Hematopoietic stem-cell transplantation or bone marrow transplantation (BMT) is the treatment of choice for young patients who have a matched sibling donor. Immunosuppression with either anti-thymocyte globulin and cyclosporine or high-dose cyclophosphamide is an effective therapy for patients who are not suitable BMT candidates owing to age or lack of a suitable donor. Results of BMT from unrelated and mismatched donors are improving, but presently this treatment option is best reserved for those patients who do not respond, relapse or develop secondary clonal disorders following immunosuppressive therapy. Efforts are currently underway to both improve immunosuppressive regimens and to expand the application of BMT.

Acceptable HLA-mismatching in unrelated donor bone marrow transplantation for patients with acquired severe aplastic anemia

We retrospectively analyzed the effect of HLA mismatching (HLA-A, -B, -C, -DRB1, -DQB1) with molecular typing on transplantation outcome for 301 patients with acquired severe aplastic anemia (SAA) who received an unrelated BM transplant through the Japan Marrow Donor Program. Additional effect of HLA-DPB1 mismatching was analyzed for 10 of 10 or 9 of 10 HLA allele-matched pairs (n = 169). Of the 301 recipient/donor pairs, 101 (33.6%) were completely matched at 10 of 10 alleles, 69 (23%) were mismatched at 1 allele, and 131 (43.5%) were mismatched at ≥ 2 alleles. Subjects were classified into 5 subgroups: complete match group (group I); single-allele mismatch group (groups II and III); multiple alleles restricted to HLA-C, -DRB1, and -DQB1 mismatch group (group IV); and others (group V). Multivariate analysis indicated that only HLA disparity of group V was a significant risk factor for poor survival and grade II-IV acute GVHD. HLA-DPB1 mismatching was not associated with any clinical outcome. We recommend the use of an HLA 10 of 10 allele-matched unrelated donor. However, if such a donor is not available, any single-allele or multiple-allele (HLA-C, -DRB1, -DQB1) mismatched donor is acceptable as an unrelated donor for patients with severe aplastic anemia.