Bone marrow transplantation for severe aplastic anemia from genotypically HLA-nonidentical relatives. An update of the Seattle experience

Anti-Thymocyte Globulin (ATG)-Free Nonmyeloablative Haploidentical PBSCT Plus Post-Transplantation Cyclophosphamide Is a Safe and Efficient Treatment Approach for Pediatric Acquired Aplastic Anemia

Most cases of acquired aplastic anemia (AA) arise from autoimmune destruction of hematopoietic stem and progenitor cells. Human leukocyte antigen (HLA)-haploidentical nonmyeloablative hematopoietic stem cell transplantation (HSCT) plus post-transplantation cyclophosphamide (PTCy) is increasingly applied to salvage AA using bone marrow as graft and anti-thymocyte globulin (ATG) in conditioning. Herein, we characterize a cohort of twelve AA patients clinically and molecularly, six who possessed other immunological disorders (including two also carrying germline SAMD9L mutations). Each patient with SAMD9L mutation also carried an AA-related rare BCORL1 variant or CTLA4 p.T17A GG genotype, respectively, and both presented short telomere lengths. Six of the ten patients analyzed harbored AA-risky HLA polymorphisms. All patients recovered upon non-HSCT (n = 4) or HSCT (n = 8) treatments. Six of the eight HSCT-treated patients were subjected to a modified PTCy-based regimen involving freshly prepared peripheral blood stem cells (PBSC) as graft and exclusion of ATG. All patients were engrafted between post-transplantation days +13 and +18 and quickly reverted to normal life, displaying a sustained complete hematologic response and an absence of graft-versus-host disease. These outcomes indicate most AA cases, including of the SAMD9L-inherited subtype, are immune-mediated and the modified PTCy-based regimen we present is efficient and safe for salvage.

Combination of Haploidentical Hematopoietic Stem Cell Transplantation with Umbilical Cord-Derived Mesenchymal Stem Cells in Patients with Severe Aplastic Anemia: a Retrospective, Controlled Study

Objective:

We retrospectively compared the outcomes of patients with severe aplastic anemia (SAA) who received haploidentical hematopoietic stem cell transplantation (haplo-HSCT) combined or not combined with umbilical cord-derived mesenchymal stem cells (UC-MSCs).

Materials and Methods:

A total of 101 patients with SAA were enrolled in this study and treated with haplo-HSCT plus UC-MSC infusion (MSC group, n=47) or haplo-HSCT alone (non-MSC group, n=54).

Results:

The median time to neutrophil engraftment in the MSC and non-MSC group was 11 (range: 8-19) and 12 (range: 8-23) days, respectively (p=0.049), with a respective cumulative incidence (CI) of 97.82% and 97.96% (p=0.101). Compared to the non-MSC group, the MSC group had a lower CI of chronic graft-versus-host disease (GVHD) (8.60±0.25% vs. 24.57±0.48%, p=0.048), but similar rates of grades II-IV acute GVHD (23.40±0.39% vs. 24.49±0.39%, p=0.849), grades III-IV acute GVHD (8.51±0.17% vs. 10.20±0.19%, p=0.765), and moderate-severe chronic GVHD (2.38±0.06% vs. 7.45±0.18%, p=0.352) were observed. The estimated 5-year overall survival (OS) rates were 78.3±6.1% and 70.1±6.3% (p=0.292) while the estimated 5-year GVHD-free, failure-free survival (GFFS) rates were 76.6±6.2% and 56.7±6.9% (p=0.045) in the MSC and non-MSC groups, respectively.

Conclusion:

In multivariate analysis, graft failure was the only adverse predictor for OS. Meanwhile, graft failure, grades III-IV acute GVHD, and moderate-severe chronic GVHD could predict worse GFFS. Our results indicated that haplo-HSCT combined with UC-MSCs infusion was an effective and safe option for SAA patients.

Comparable Outcomes in Acquired Severe Aplastic Anemia Patients With Haploidentical Donor or Matched Related Donor Transplantation: A Retrospective Single-Center Experience

Clinical data of patients with severe aplastic anemia (SAA) were retrospectively analyzed to evaluate the outcomes of haploidentical hematopoietic stem cell transplantation (HID-HSCT) with matched related sibling hematopoietic stem cell transplantation (MSD-HSCT) in complications and survivals. Thirty consecutive patients were enrolled in the study with a median follow-up of 50 months (range 4, 141), and the median age of the patients was 21 years (range 3, 49). All the patients achieved myeloid engraftment in the two cohorts. The cumulative incidences of platelet engraftment were 95.5 and 100% in HID cohort and MSD cohort, respectively. The median time for neutrophil and platelet recovery was 11 (range 9, 19) and 15 (range 10, 25) days in HID cohort, and 12 (range 10, 19) and 14 (range 8, 25) days in MSD cohort. The cumulative incidences of grade II–IV and grade III–IV acute graft vs. host disease (aGvHD) in HID cohort and in MSD cohort were 18.9 vs. 14.3% (p = 0.77) and 10.5 vs. 0% (p = 0.42), respectively. The cumulative incidences of chronic graft vs. host disease (cGvHD) was 22.7% in HID cohort and 25.5% in MSD cohort (p = 0.868). The 5-year overall survival (OS) rates and 5-year failure-free survival (FFS) rates in HID cohort and MSD cohort were 85.1 vs. 87.5% (p = 0.858), 80.3 vs. 87.5% (p = 0.635), respectively. The median time to achieve engraftment, cumulative incidence of aGvHD and cGvHD, and the 5-year OS and FFS rates were not significantly different between the two cohorts. We suggest that HID-HSCT might be a safety and effective option for SAA patients without a matched donor.

Optimizing outcomes for haploidentical hematopoietic stem cell transplantation in severe aplastic anemia with intensive GVHD prophylaxis: a review of current findings

Introduction: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has resulted in increased levels of disease-free survival in severe aplastic anemia (SAA). Haploidentical transplantation (haplo-SCT) was previously not recommended due to unacceptable incidences of graft-versus-host disease (GvHD) and graft failures. With the advent of intensive GvHD prophylaxis strategies, the outcomes obtained with haplo-SCT for SAA have gradually improved.Areas covered: A comprehensive search considered PubMed reported articles before 1 February 2021, presented abstracts, and clinical trials pertaining to haplo-HSCT for SAA. This manuscript covers modern approaches with intensive GvHD prophylaxis in haplo-SCT for SAA. The representative methods consist of granulocyte colony stimulating factor (G-CSF) plus ATG-based and posttransplantation cyclophosphamide (PT-Cy)-based protocols.Expert opinion: Currently, haplo-SCT has become a feasible option for treating SAA. The G-CSF/ATG-based protocol included the largest sample size and reported comparable survival rates with identical siblings. The PT-Cy protocol resulted in a relatively lower incidence of GvHD and seemingly poorer but continuously improved engraftment with augmented conditioning. The optimized outcomes are constantly updated with the modification of the conditioning regimen, donor selection, graft source and GvHD prophylaxis. In the future, we should pay more attention to quality of life in addition to survival, and personalized haplo-SCT may improve outcomes.

Haploidentical stem cell transplantation for aplastic anemia: the current advances and future challenges

Haematopoietic stem cell transplantation (HSCT) is a curative option for severe aplastic anemia (SAA). Finding a suitable matched donor in a timely manner is a challenge. The availability of haploidentical donors and their successful use in transplantation have expanded valid choices for SAA. In recent decades, haploidentical HSCT (haplo-HSCT) for the treatment of SAA has been continuously attempted, and great strides have been made. Nowadays, haplo-HSCT using different regimens has overcome the difficulty of graft failure and severe graft-versus-host disease (GvHD), and achieved inspiring survival outcomes in SAA. The regimens consist mainly of granulocyte colony-stimulating factor (G-CSF) plus antithymocyte globulin (ATG), posttransplantation cyclophosphamide (PT-Cy), and ex vivo graft T-cell depletion (TCD). In particular, the G-CSF and ATG-based regimen includes the largest sample size and the successful wide use of the G-CSF and ATG-based regimen has promoted haplo-HSCT a higher priority in SAA patients without matched related or unrelated donors in China. Recent studies have also indicated that haplo-HSCT using PT-Cy or TCD regimen is a practicable alternative, but the sample size is relatively small. Here, we offer an overview of clinical results obtained through the use of haploidentical transplantation in SAA, mainly focusing on current advances and future challenges.

Outcomes of Haploidentical Stem Cell Transplantation using Total Body Irradiation (600 cGy) and Fludarabine with Antithymocyte Globulin in Adult Patients with Severe Aplastic Anemia: A Prospective Phase II Study

The aim of this study was to verify the feasibility of rabbit antithymocyte globulin (ATG; 5 mg/kg) in combination with 600 cGy of fractionated total body irradiation (fTBI; 3 doses of 200 cGy) and fludarabine (Flu; 150 mg/m²) as a conditioning regimen for haploidentical stem cell transplantation from a related mismatched donor (haplo-SCT) in adult patients with severe aplastic anemia (SAA). We analyzed 47 consecutive patients who underwent haplo-SCT, including 24 patients from our previous pilot report. The median age was 36.0 years (range, 17 to 61 years), and 25 patients (53%) were very severe aplastic anemia (VSAA) at transplantation. All patients achieved primary engraftment. The cumulative incidence of grade ≥II acute graft-versus-host disease (GVHD) and chronic moderate or greater GVHD was 27.7% at 100 days and 13.5% at 3 years, respectively. With a median follow-up of 32.3 months, the 3-year probability of overall survival and failure-free survival was 91.0% and 88.6%, respectively. The 3-year GVHD- and failure-free survival (GFFS) was 71.6%. Offspring donor and lower comorbidity index were independent factors correlated with higher GFFS in multivariate analysis. In conclusion, the outcomes of haplo-SCT with fTBI 600 cGy/Flu/ATG-5 indicate that haplo-SCT can be an effective alternative option when a fully matched donor is not available or a patient with VSAA needs an urgent transplantation.

Therapeutic Outcomes of Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation in Patients With Severe Aplastic Anemia: A Multicenter Study

BACKGROUND

Haploidentical donor (HID) allogeneic hematopoietic stem cell transplantation (HSCT) is an alternative curative treatment for patients with severe aplastic anemia (SAA) who do not have suitable matched related donors (MRD). The aim of this study was to compare the therapeutic outcomes of HID-HSCT with those of MRD-HSCT for SAA.

METHODS

A total of 235 SAA patients who underwent HID-HSCT (116) or MRD-HSCT (119) at 11 transplantation centers from January 2007 to January 2016 were included. Complications and survival outcomes were evaluated and compared between the 2 groups.

RESULTS

The HID group had a lower incidence of secondary graft failure but higher incidences of acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD). However, the incidence of severe aGVHD (grades III-IV), poor graft function, and infections was comparable between groups. Patients in the HID group had a significantly lower survival and overall survival rates than those in the MRD group. The estimated 3-year survival rates for the MRD and HID groups were 82.82% and 75.00%, respectively. Ferritin levels, graft failure, poor graft function, severe aGVHD, and infections were the significant risk factors for survival.

CONCLUSIONS

The overall survival rate is acceptable for patients who underwent HID-HSCT, making it a feasible treatment choice for SAA patients.

Optimal conditioning regimen for haplo-identical stem cell transplantation in adult patients with acquired severe aplastic anemia: Prospective de-escalation study of TBI and ATG dose

This prospective study explored an optimal conditioning regimen to ensure engraftment with minimal toxicity in adult patients with severe aplastic anemia (SAA) who received haplo-identical stem cell transplantation from a related mismatched donor (Haplo-SCT). We explored a safe and sufficient dose of rabbit ATG (Thymoglobulin) in combination with 800 cGy total body irradiation (TBI) and fludarabine (Flu, 30 mg/m² /day) for 5 days using step-by-step dose de-escalation. The dose of ATG was de-escalated from 10 mg/kg (group 1), to 7.5 mg/kg (group 2), to 5 mg/kg (group 3), and the TBI dose was reduced to 600 cGy (group 4) beginning in October 2014. If one patient developed transplant-related mortality (TRM) with engraftment in a group, we moved to the next lower dose group. Thirty-four patients were enrolled in groups 1-3 (n = 10) and 4 (n = 24). All patients achieved primary engraftment. The incidence of acute GVHD (grade ≥ 2) and chronic GVHD (≥ moderate) was 29.4% and 14.7%, respectively. With a median follow-up of 56.6 and 21.8 months in groups 1-3 and group 4, respectively, the 2-year probability of overall survival (91.7% in group 4 vs 70% in groups 1-3, P = 0.155) and GVHD-free survival (78.4% in group 4 vs 50% in groups 1-3, P = 0.115) was shown tended to be better in group 4. This study explored an optimal conditioning with step-by-step de-escalation dosage of ATG and TBI to reduce TRM with sustained graft function. TBI-600 cGy/Flu/intermediate-dose ATG resulted in feasible outcomes of Haplo-SCT for adult patients with SAA.

Donor-derived marrow mesenchymal stromal cell co-transplantation following a haploidentical hematopoietic stem cell transplantation trail to treat severe aplastic anemia in children

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is associated with an increased risk of graft failure and severe graft-versus-host disease (GVHD). Recent studies have shown that mesenchymal stromal cells (MSCs) display potent immunosuppressive effects and can support normal hematopoiesis. In a multi-center trial, we co-transplanted culture-expanded donor-derived bone marrow MSCs (BM-MSCs) into 35 children with severe aplastic anemia (SAA) undergoing haplo-HSCT. All 35 patients (100%) achieved hematopoietic reconstitution and showed sustained full donor chimerism. The median time for myeloid engraftment was 14 days (range 10-22 days), while that for platelet engraftment was 18 days (range 9-36 days). The incidence of grade II-IV acute GVHD and chronic GVHD was 25.71 and 22.86%, respectively. The overall survival rate was 85.71% with a median of 22 months (range 3.5-37 months). The combined transplantation of haploidentical HSCs and BM-MSCs into children with SAA without an HLA-identical sibling donor is relatively safe and may represent an effective new therapy to improve survival rates and reduce the risk of graft failure.

Optimal donor for severe aplastic anemia patient requiring allogeneic hematopoietic stem cell transplantation: A large-sample study from China

HLA-haploidentical hematopoietic stem cell transplantation (HSCT) may be an option for severe aplastic anemia (SAA) patients. However, to date, no large-sample studies have been performed to determine which types of SAA patients are suitable for HLA-haploidentical HSCT. We retrospectively studied 189 consecutive patients with SAA who underwent HLA-identical or HLA-haploidentical HSCT at seven transplant centers in China. Propensity score matching (PSM) was applied in this study to reduce the influence of potential confounders. The 5-year overall survival (OS) rate was 72.0% in the HLA-haploidentical group and 76.5% in the HLA-identical group. The median time to achieve engraftment and the incidence of acute GVHD/chronic GVHD were not significantly different between the two groups. In the subgroup analysis, the outcome of patients older than 40 years in the HLA-haploidentical group was significantly poorer than that of patients younger than 40 years in the same group and that of patients older than 40 years in the HLA-identical group. Based on the above results, we suggest that HLA-haploidentical relative HSCT should be considered as a valid alternative option for patients younger than 40 years with SAA for whom no matched sibling donor is available.

Unmanipulated haploidentical transplantation conditioning with busulfan, cyclophosphamide and anti-thymoglobulin for adult severe aplastic anaemia

We conducted a retrospective analysis to evaluate outcomes of haploidentical transplantation in adult severe aplastic anaemia (SAA) patients. Fifty-one adults received haploidentical transplantation between May 2011 and December 2016. Patients were administered busulfan (Bu), cyclophosphamide (Cy) and anti-thymoglobulin (ATG) as conditioning regimens, followed by bone marrow and peripheral blood transplantation. The patients' median age was 25 years. Forty-nine patients survived for more than 28 days and all achieved donor myeloid engraftment. The median time for myeloid engraftment and platelet recovery was 13 days (range, 10-21) and 17.5 (range, 7-101) days. The cumulative incidence (CI) of grade II-IV and III-IV acute GvHD) was 20.00±0.33% and 6.00±0.12%, respectively. The incidence of chronic GvHD was 14.00±0.36% and 25.90±0.71%, and that of moderate-severe chronic GvHD was 2.51±0.06% and 6.92±0.25% at 1 and 3 years, respectively. The 3-year estimated overall survival and failure-free survival were both 83.5±5.4% with a median follow-up of 21.1 months. Multivariate analysis showed hematopoietic cell transplantation-specific comorbidity index (HCT-CI) score of ⩾3 was significantly associated with worse outcome. Haploidentical transplantation conditioning including Bu/Cy/ATG was a safe and effective strategy for adult SAA patients, and HCT-CI might be an outcome predictor in these patients.

Upfront haploidentical transplant for acquired severe aplastic anemia: registry-based comparison with matched related transplant

BACKGROUND

Haploidentical donor (HID) hematopoietic stem cell transplantation (HSCT) is an alternative treatment method for severe aplastic anemia (SAA) patients lacking suitable identical donors and those who are refractory to immunosuppressive therapy (IST). The current study evaluated the feasibility of upfront haploidentical HSCT in SAA patients.

METHODS

We conducted a multicenter study based on a registry database. One hundred fifty-eight SAA patients who underwent upfront transplantation between June 2012 and September 2015 were enrolled.

RESULTS

Eighty-nine patients had haploidentical donors (HIDs), and 69 had matched related donors (MRDs) for HSCT. The median times for myeloid engraftment in the HID and MRD cohorts were 12 (range, 9-20) and 11 (range, 8-19) days, with a cumulative incidence of 97.8 and 97.1% (P = 0.528), respectively. HID recipients had an increased cumulative incidence of grades II-IV acute graft-versus-host disease (aGVHD) (30.3 vs. 1.5%, P < 0.001), grades III-IV aGVHD (10.1 vs. 1.5%, P = 0.026), and chronic GVHD (cGVHD) (30.6 vs. 4.4%, P < 0.001) at 1 year but similar extensive cGVHD (3.4 vs. 0%, P = 0.426). The three-year estimated overall survival (OS) rates were 86.1 and 91.3% (P = 0.358), while the three-year estimated failure-free survival (FFS) rates were 85.0 and 89.8% (P = 0.413) in the HID and MRD cohorts, respectively. In multivariate analysis, survival outcome for the entire population was significantly adversely associated with increased transfusions and poor performance status pre-SCT. We did not observe differences in primary engraftment and survival outcomes by donor type.

CONCLUSIONS

Haploidentical SCT as upfront therapy was an effective and safe option for SAA patients, with favorable outcomes in experienced centers.

[HLA- haploidentical donor hematopoietic transplantation for severe aplastic anemia achieved comparable outcomes with HLA- unrelated donor transplantation]

目的

评价亲缘半相合造血干细胞移植（Haplo-HSCT）治疗重型再生障碍性贫血（SAA）的疗效，并且与同期进行的无关供者造血干细胞移植（UD-HSCT）进行比较。

方法

回顾性分析2012年9月至2014年7月接受替代供者造血干细胞移植的50例SAA患者临床资料；其中24例接受Haplo-HSCT, 26例接受UD-HSCT。

结果

中位随访时间9(2~26)个月，总生存（OS）率为91.3%。UD-HSCT组和Haplo-HSCT组OS率分别为96.1%和86.0%（P=0.30）。3例（6%）患者原发植入失败。Haplo-HSCT组患者Ⅱ~Ⅳ度急性移植物抗宿主病、慢性移植物抗宿主病、CMV血症、EBV血症发生率分别为37.5%、37.5%、78.2％及43.1%，均明显高于UD-HSCT组（3.83%、15.3%、46.1％及16.0%）（P值分别为0.003、0.030、0.005、0.040）；出血性膀胱炎发生率差异无统计学意义（39.1％对23.0%，P=0.120）。

结论

Haplo-HSCT治疗SAA OS率较高，疗效与UD-HSCT相近。

Haplo-identical transplantation for acquired severe aplastic anaemia in a multicentre prospective study

We conducted a prospective, multicentre study to confirm the feasibility of haplo-identical transplantation in treatment of severe aplastic anaemia (SAA) as salvage therapy, by analysing the outcomes of 101 patients who received haplo-identical transplantation between June 2012 and October 2015. All cases surviving for more than 28 d achieved donor myeloid engraftment. The median time for myeloid engraftment was 12 (range, 9-25) days and 15 (range, 7-101) days for platelets, with a cumulative platelet engraftment incidence of 94·1 ± 0·1%. With a median follow-up of 18·3 (3·0-43·6) months, recipients from haplo-identical transplantation had more cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD, 33·7% vs. 4·2%, P < 0·001), more chronic GVHD (22·4% vs. 6·6%, P = 0·014) at 1 year, but similar grade III-IV aGVHD (7·9% vs. 2·1%, P = 0·157), 3-year estimated overall survival (OS, 89·0% vs. 91·0%, P = 0·555) and failure-free survival (FFS, 86·8% vs. 80·3%, P = 0·659) when compared with 48 patients who received contemporaneous transplantation from matched related donors. Multivariate analysis showed no significant difference in engraftment and survival between the two cohorts. Both OS and FFS for the entire population correlated significantly with grades III-IV aGVHD. In conclusion, haplo-identical transplantation is a feasible choice for SAA with favourable outcomes.

Recent advances in treatment of aplastic anemia

Recent advances in the treatment of aplastic anemia (AA) made most of patients to expect to achieve a long-term survival. Allogeneic stem cell transplantation (SCT) from HLA-matched sibling donor (MSD-SCT) is a preferred first-line treatment option for younger patients with severe or very severe AA, whereas immunosuppressive treatment (IST) is an alternative option for others. Horse anti-thymocyte globuline (ATG) with cyclosporin A (CsA) had been a standard IST regimen with acceptable response rate. Recently, horse ATG had been not available and replaced with rabbit ATG in most countries. Subsequently, recent comparative studies showed that the outcomes of patients who received rabbit ATG/CsA were similar or inferior compared to those who received horse ATG/CsA. Therefore, further studies to improve the outcomes of IST, including additional eltrombopag, are necessary. On the other hand, the upper age limit of patients who are able to receive MSD-SCT as first-line treatment is a current issue because of favorable outcomes of MSD-SCT of older patients using fludarabine-based conditioning. In addition, further studies to improve the outcomes of patients who receive allogeneic SCT from alternative donors are needed. In this review, current issues and the newly emerging trends that may improve their outcomes in near futures will be discussed focusing the management of patients with AA.

Good outcome of haploidentical hematopoietic SCT as a salvage therapy in children and adolescents with acquired severe aplastic anemia

Haploidentical hematopoietic SCT (haplo-HSCT) is to be established in patients with acquired severe aplastic anemia (SAA) refractory to immunosuppressive therapy and lacking HLA-matched related or unrelated donors. Graft failure (GF) and GVHD have been major obstacles to HSCT. A total of 17 children and adolescents with SAA underwent haplo-HSCT in our center. The conditioning regimen consisted of BU, fludarabine, CY and anti-thymocyte globulin. All patients received cyclosporine, short-term MTX, mycophenolate mofetil and basiliximab for GVHD prophylaxis. Mesenchymal stem cells derived from unrelated umbilical cord were infused on day 1. Neutrophil engraftment was achieved in all 17 patients in a median time of 16 days (range 9-25 days). The median time of platelet engraftment was 22 days (range 9-95 days) in 16 patients. The cumulative incidence (CI) of II-IV acute GVHD (aGVHD) at day +100 was 30.53±11.12% and III-IV aGVHD occurred in only one patient. The CI of chronic GVHD was 21.25±13.31%. Secondary GF with autologous hematopoiesis recovery occurred in one patient. The OS was 71.60±17.00% at a median follow-up of 362 (36-1321) days. These limited promising data suggest that haplo-HSCT is feasible as a salvage therapy for children and adolescents with refractory SAA who lack matched donors.

Haematopoietic stem cell transplantation for acquired aplastic anaemia

PURPOSE OF REVIEW

Survival outcomes from haematopoietic stem cell transplantation (HSCT) in severe aplastic anaemia (SAA) have improved steadily over the past decades, largely reflecting progress in supportive care and conditioning regimens. Here we review recently published data that highlight the improvements and current issues.

RECENT FINDINGS

Human leukocyte antigen (HLA)-matched sibling donor (MSD) HSCT remains the gold standard for SAA patients younger than 40-50 years, with HLA-matched unrelated donor (MUD) HSCT for second line after failure to respond to immunosuppressive therapy (IST). The use of alternative donor sources for aplastic anaemia patients remains limited and problematic, but novel conditioning regimens, particularly in the haploidentical setting, justify further evaluation. In recent studies when comparing alemtuzumab-based conditioning with standard antithymocyte globulin conditioning regimens, lower rates of acute and chronic graft-versus-host disease and better tolerance in older patients are seen.

SUMMARY

Improving outcomes may lead to an expanded frontline HSCT role in the future. In children lacking a MSD, increasingly MUD HSCT is being considered as first-line treatment and is also being considered more for young adults. Further research is needed to advance our understanding of the role HSCT has to play in SAA with particular emphasis on alternative donor sources and identifying optimal conditioning regimens.

Long-term outcome of HLA-haploidentical hematopoietic SCT without in vitro T-cell depletion for adult severe aplastic anemia after modified conditioning and supportive therapy

HLA-haploidentical hematopoietic SCT (HSCT) is an option for severe aplastic anemia (SAA) patients. Here, we evaluated the outcomes of 26 adult-SAA patients who received HLA-haploidentical HSCT in five transplant centers in southwestern China. Most of the patients in this study failed prior therapy and were transfused heavily before the transplantation. The patients received fludarabine+cyclophosphamide+antithymocyte globulin as conditioning regimens and then unmanipulated peripheral blood plus marrow transplantation. Micafungin, i.v. Ig and recombinant human TPO were used for post-grafting infection prevention and supportive care. Of 26 patients, 25 achieved engraftment at a median of 13 days (range, 11-19 days) after HSCT. One of 25 patients experienced graft rejection and did not achieve sustained engraftment after second HSCT. Therefore, the final engraftment rate was 92.3%. Three of 25 (12%) patients developed acute GVHD, 10 of 25 (40%) patients developed chronic GVHD (9 with limited whereas the other with extensive). The OS rate was 84.6% and the average follow-up time was 1313.2 (738-2005) days for surviving patients. This encouraging result suggests that HLA-haploidentical HSCT is an effective therapeutic option for adults with acquired SAA if an HLA-identical donor is not available.

Cotransplantation of haploidentical hematopoietic and umbilical cord mesenchymal stem cells for severe aplastic anemia: successful engraftment and mild GVHD

Haploidentical hematopoietic stem-cell transplantation (haplo-HSCT) is associated with an increased risk of graft failure and severe graft-versus-host disease (GVHD). Mesenchymal stromal cells (MSCs) have been shown to support in vivo normal hematopoiesis and to display potent immunesuppressive effects. We cotransplanted the culture-expanded third-party donor-derived umbilical cord MSCs (UC-MSCs) in 21 young people with severe aplastic anemia (SAA) undergoing haplo-HSCT without T-cell-depleted. We observed that all patients had sustained hematopoietic engraftment without any adverse UC-MSC infusion-related events. Furthermore, we did not observe any increase in severe aGVHD. These data suggest that UC-MSCs, possibly thanks to their potent immunosuppressive effect on allo-reactive host T lymphocytes escaping the preparative regimen, reduce the risk of graft failure and severe GVHD in haplo-HSCT.

Haploidentical transplantation in patients with acquired aplastic anemia

Haploidentical SCT (haplo-SCT) has been considered a therapeutic option in patients with acquired severe aplastic anemia (SAA) failing at least one course of immune suppressive therapy with antithymocyte globulin and lacking an HLA-matched related or unrelated donor. The platforms of both ex vivo T-cell-depleted and unmanipulated grafts have been explored in children and adults. Overall, the primary objective of a stable haploidentical hematopoietic engraftment with a low rate of GVHD is unmet in a significant proportion of patients undergoing haplo-SCT for SAA. Haploidentical transplants for refractory SAA should be performed in a specialist center with major experience in hematopoietic SCT procedures and preferably performed within the framework of a local clinical protocol designed specifically to address the prevention of graft rejection and GVHD.

A novel protocol for haploidentical hematopoietic SCT without in vitro T-cell depletion in the treatment of severe acquired aplastic anemia

Mismatched related donors of hematopoietic SCT (HSCT) for severe aplastic anemia (SAA) present challenges mainly associated with graft failure and GVHD. The greater the HLA disparity, the poorer the OS. About 19 consecutive SAA/very SAA (VSAA) patients who received HSCT from haploidentical family donors in our center are reported in this study, 18/19 pairs had 2-3 loci mismatched. All 19 cases failed to respond to previous therapy and were heavily transfused before transplantation. The conditioning regimen before HSCT included BU, CY and thymoglobulin. The recipients received CsA, mycophenolate mofetil (MMF) and short-term MTX for GVHD prophylaxis. The source of stem cell grafts was a combination of G-CSF-primed BM and G-CSF-mobilized peripheral blood stem cells. All patients achieved 100% donor myeloid engraftment; the median time for myeloid engraftment was 12 days (ranging from 10-29 days) and for platelets was 18 days (ranging from 8-180 days) with a cumulative platelet engraftment incidence of 84.21 ± 10.53%. The cumulative incidence was 42.1 ± 11.3% for grade II-IV acute GVHD and 56.2 ± 12.4% for chronic GVHD. The OS was 64.6 ± 12.4% with a median 746-day (90-1970) follow-up for surviving patients. These limited retrospective analysis data suggest that HLA-haploidentical HSCT for SAA patients without an HLA-identical sibling donor might be feasible. Further research to increase OS by decreasing GVHD while maintaining stable engraftment will be needed in the future.

Hematopoietic stem cell transplantation for bone marrow failure syndromes in children

Bone marrow failure (BMF) syndromes include a broad group of diseases of varying etiologies, in which hematopoeisis is abnormal or completely arrested in one or more cell lines. BMF can be an acquired aplastic anemia (AA) or can be congenital, as part of such syndromes as Fanconi anemia (FA), Diamond Blackfan anemia, and Schwachman Diamond syndrome (SDS). In this review, we first address the evolution and current status of bone marrow transplantation (BMT) in the pediatric population in the most common form of BMF, acquired AA. We then discuss pediatric BMT in some of the more common inherited BMF syndromes, with emphasis on FA, in which experience is greatest. It is important to consider the possibility of a congenital etiology in every child (and adult) with marrow failure, because identification of an associated syndrome provides insight into the likely natural history of the disease, as well as prognosis, treatment options for the patient and family, and long-term sequelae both of the disease itself and its treatment.

Salvage transplantation for allograft failure using fludarabine and alemtuzumab as conditioning regimen

Graft failure after allogeneic blood or marrow transplantation, although generally uncommon, can be a devastating complication. This report includes the outcome of nine patients who received a salvage transplant for failure to engraft after one (n=8) or 2 (n=1) prior transplants. Eight patients received allografts from the original donor. All received fludarabine 30 mg/m(2) i.v. and alemtuzumab 20 mg i.v. daily from days -6 to -2. Daily CYA was begun on day -2, and the allograft was infused on day 0. The therapy was well tolerated with low toxicity, and all nine patients engrafted, recovering neutrophils at a median of 12 days after transplant. Four patients died: two of relapse, one of a fungal infection in the setting of GVHD and one of multiple sclerosis. The combination of fludarabine and alemtuzumab is an effective and well-tolerated salvage conditioning regimen for patients who experience graft failure after blood or marrow transplants.

Recent improvement in outcome of unrelated donor transplantation for aplastic anemia

The aim was to determine whether outcome of unrelated donor transplantation for severe aplastic anemia has improved in recent years and whether this is due to patient selection or better transplant technology. We analyzed 498 patients transplanted during 1990-2005. By running univariate regression models dichotomizing year of transplantation we defined 1998 as the year of the most significant change in survival. Five-year survival increased from 32+/-8% before 1998 to 57+/-8% after 1998 (P<0.0001). When comparing the cohort before (n=149) and after 1998 (n=349), there were no differences except for older age, and more frequent use of PBSCs, after 1998. High-resolution HLA typing data were unavailable. After 1998, there was less graft failure (11 vs 26%, P<0.0001), less acute GvHD (cumulative incidence 28 vs 37%, P=0.02) and less chronic GvHD (22 vs 38%, P=0.004). In multivariate analyses adjusting for differences in age, HLA-mismatch, performance score and time to transplantation, there was no change in the year of transplant effect (relative risk of death in transplants after 1998: 0.44 (95% confidence interval 0.33-0.59)). There is no evidence for patient selection to explain significantly improved survival in patients transplanted after 1998. We speculate that this is due to better donor matching.

Allogeneic stem cell transplantation for aplastic anemia

Aplastic anemia encompasses a heterogeneous group of diseases with distinct pathophysiologies and a common clinical endpoint of marrow failure. Patients with severe aplastic anemia can be treated with immunosuppressive therapy (IST) or hematopoietic stem cell transplantation (HSCT). Over the last 30 years, advances in both treatment modalities have significantly improved the prognosis for this disease; yet this evolution complicates the central therapeutic question in aplastic anemia: which patients should receive IST and which ones should receive HSCT as front-line therapy? In this review, we describe the major improvements that have occurred in transplantation for aplastic anemia in the last 3 decades. We then outline a framework for deciding which patients should be considered for upfront transplantation.

Bone marrow transplantation in children with severe aplastic anemia using a conditioning regimen containing 3 Gy of total body irradiation, cyclophosphamide with or without antithymocyte globulin

We have employed the 3 Gy total body irradiation (TBI) containing conditioning regimen to bone marrow transplantation (BMT) for severe aplastic anemia (SAA) in pediatric patients irrespective of donor type since March 1986. The outcome of BMT for 17 SAA patients is favorable. Eight patients received BMT from human leukocyte antigen matched-related donors (MRD) and nine received BMT from alternative donors. The conditioning regimen consisted of 3-Gy TBI and cyclophosphamide of 200 mg/kg in the BMT from MRD. In the case of BMT from alternative donor, antithymocyte globulin 10 mg/kg was added to the regimen. Fifteen of 17 patients (88%) engrafted on median of day 18 (range, 11-26) and all 13 evaluable patients showed complete donor chimerism by median 30 (range, 13-47) days after BMT. Fourteen patients have survived with a median follow-up of 67 (range, 2-228) months and the probability of survival was 81.9% (95% CI, 63.3-100%). No late complications including second malignancies caused by TBI have been observed and all three female patients have regular menstruation. In conclusion, TBI of 3 Gy appears to be an appropriate dose regarding to ensure engraftment and avoid the risk of late adverse event for SAA patients.

Comparable Outcomes of Matched-Related and Alternative Donor Stem Cell Transplantation for Pediatric Severe Aplastic Anemia

Matched sibling donor (MSD) bone marrow transplantation is the treatment of choice for pediatric patients with severe aplastic anemia (SAA); however, only about 33% of patients will have an HLA-identical sibling. Alternative donor (AD) transplants may be an option for these patients, but such therapies have been associated with greater incidence of graft failure and graft-versus-host disease (GVHD). We retrospectively analyzed 36 pediatric patients who received 38 bone marrow or peripheral blood stem cell transplants (15 MSD and 23 AD) for SAA at our institution from April 1997 to October 2005. Nineteen AD recipients received reduced intensity conditioning with cyclophosphamide, low-dose total body irradiation, and antithymocyte globulin (ATG) or Campath. The 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients treated with reduced intensity conditioning regimens at a median follow-up of 52 months (range, 6-99 months). No patient receiving Campath, compared with 3 of 9 patients receiving ATG, developed extensive, chronic GVHD. We conclude that, for children with SAA, AD transplantation is as effective as MSD transplantation. Further, compared with ATG, preparatory regimens containing Campath may be associated with a lower incidence of extensive, chronic GHVD.

Bone marrow transplants from mismatched related and unrelated donors for severe aplastic anemia

For patients with acquired severe aplastic anemia without a matched sibling donor and not responding to immunosuppressive treatment, bone marrow transplantation from a suitable alternative donor is often attempted. We examined risks of graft failure, graft-versus-host disease and overall survival after 318 alternative donor transplants between 1988 and 1998. Sixty-six patients received allografts from 1-antigen and 20 from >1-antigen mismatched related donors; 181 from matched and 51 from mismatched unrelated donors. Most patients were young, had had multiple red blood cell transfusions and poor performance score at transplantation. We did not observe differences in risks of graft failure and overall mortality by donor type. The probabilities of graft failure at 100 days after 1-antigen mismatched related donor, >1-antigen mismatched related donor, matched unrelated donor and mismatched unrelated donor transplants were 21, 25, 15 and 18%, respectively. Corresponding probabilities of overall survival at 5 years were 49, 30, 39 and 36%, respectively. Although alternative donor transplantation results in long-term survival, mortality rates are high. Poor performance score and older age adversely affect outcomes after transplantation. Therefore, early referral for transplantation should be encouraged for patients who fail immunosuppressive therapy and have a suitable alternative donor.

Haematopoietic stem cell transplantation to treat aplastic anaemia

Aplastic anaemia (AA) consists of pancytopenia and empty bone marrow. Its incidence varies worldwide but predominates in developing countries. Diverse aetiologies are involved, with autoimmunity at the centre of the picture. For the 70% of patients with the severe and very severe forms of AA and who lack a human leukocyte antigen (HLA)-matched sibling, immunosuppressive therapy (IST) is key in treating the disease, with a remission rate close to 70%, an 80-90% 5-year survival rate in responding patients and a relapse rate close to 10%. For the 30% with a sibling donor available, haematopoietic stem cell transplant (HSCT) from bone marrow or peripheral blood has up to a 90% chance of cure, with a 5-10% graft rejection/failure rate. Patients who fail IST (25-30%) and lack a sibling donor can benefit from CD34(+)-enriched, partially T cell-depleted unrelated stem cell transplants, with a general survival rate up to 37%, the newest source of stem cells for this modality being cord blood. Non-myeloablative, irradiation-free conditioning regimens offer appreciable benefits, and new immunosuppressive agents, such as fludarabine and alemtuzumab, have been incorporated with promising preliminary results. Graft-versus-host disease, graft failure and infections remain significant challenges in HSCT for which innovative treatment strategies are being developed at present.

Non-total body irradiation containing preparative regimen in alternative donor bone marrow transplantation for severe aplastic anemia

Using non-total body irradiation (TBI) containing preparative regimens, 13 patients with severe aplastic anemia (SAA) were transplanted from an alternative donor in a single institute. In total, 12 donors were unrelated volunteers and one was an HLA one-locus mismatched sibling. Median time from diagnosis of SAA to bone marrow transplantation (BMT) was 10.1 months (range, 1.6-180.1). Nine patients had received immunosuppressive treatment with ATG before BMT, while four had not. Preparative regimens consisted of cyclophosphamide plus ATG in nine patients, cyclophosphamide plus fludarabine in two patients, and cyclophosphamide plus fludarabine plus ATG in two patients. All patients received non-T-cell depleted bone marrow from the donor. Cyclosporine plus methotrexate were given for GVHD prophylaxis. All patients engrafted on a median of day 21 (range, 15-27). Grade III-IV acute GVHD developed in three (23%) of 13 patients and extensive chronic GVHD in four (31%) of 12 evaluable patients. With a median follow-up duration of 1138 days (range, 118-1553), 10 patients are alive with durable engraftment showing 74.6% (95% confidence interval, 49.5-99.7%) of survival rate. Cause of the deaths was CNS bleeding in one and chronic GVHD in two. In conclusion, non-TBI containing preparative regimen could ensure durable engraftment in alternative donor BMT for SAA and showed promising results.

Successful non-T-cell-depleted nonmyeloablative hematopoietic stem cell transplantation (NST) from an HLA-haploidentical 2-loci-mismatched sibling in a heavily transfused patient with severe aplastic anemia based on the fetomaternal microchimerism

A 37-year-old Japanese man with systemic hemochromatosis due to multiple transfusions was referred to us for the treatment of severe aplastic anemia (SAA), from which he had been suffering for 24 years. The patient had diabetes arising from the hemochromatosis, chronic anal fissures, and a kidney abscess due to neutropenia. He was treated with a nonmyeloablative preconditioning regimen followed by non-T-cell-depleted (non-TCD) allogeneic peripheral blood stem cell transplantation (PBSCT) from his human leukocyte antigen (HLA)-haploidentical 2-loci-mismatched sibling. Prompt engraftment of granulocytes and platelets was observed, and graft-versus-host disease was easy to control. Noninherited maternal antigens in the donor were confirmed prior to PBSCT, and they were also detected in small quantities in the recipient. This report describes the first successful nonmyeloablative hematopoietic stem cell transplant in a heavily transfused SAA patient from an HLA-haploidentical 2-loci-mismatched sibling donor. The result suggests that a long-term fetomaternal microchimerism-positive sibling can be a second-line donor if an alternative HLA-identical donor is not available.

Marrow transplants from matched unrelated donors for aplastic anaemia using alemtuzumab, fludarabine and cyclophosphamide based conditioning

Graft failure, regimen-related toxicity and graft-versus-host disease (GVHD) are the critical barriers to unrelated donor transplants for aplastic anaemia (AA). We investigated the use of a novel conditioning regimen consisting of alemtuzumab (humanized CD52 antibody), fludarabine and cyclophosphamide in seven patients with AA, who underwent bone marrow transplant procedure using matched unrelated donors. The aetiology of AA was acquired (n=3), Fanconi's (n=3) and congenital (n=1). Median age was 13 years (range 8-35). All the donors were fully matched for HLA class I and II antigens using high-resolution typing. All the patients engrafted at a median of 18 days (range 13-35). Two patients died of transplant-related complications: one of adenovirus disease and the other developed extensive chronic GVHD of skin followed by cytomegalovirus (CMV) disease. Three patients developed Grade II acute GVHD disease (GVHD); none had Grade III-IV acute GVHD. Of the six evaluable patients, only one developed chronic GVHD. We conclude that this conditioning regimen for unrelated donor transplants for AA is sufficiently immunosuppressive to allow stable engraftment and appears to have a favourable impact on the incidence and severity of GVHD, warranting further investigation.

Unrelated donor bone marrow transplantation for children with severe aplastic anemia: minimal GVHD and durable engraftment with partial T cell depletion

Both increased graft rejection and increased graft vs host disease (GVHD) remain obstacles to success for unrelated donor (URD) BMT for patients with SAA. Partial T cell depletion (PTCD) may decrease the risk of severe GVHD, while still maintaining sufficient donor T lymphocytes to ensure engraftment. We report on 12 patients with SAA who underwent PTCD URD BMT. All patients had failed medical therapy or relapsed following initial responses, and were transfusion dependent. The median age was 6 years, and there were five males. Donors were matched for four patients, and mismatched for eight. All patients received total body irradiation with either Ara-C or thiotepa and cyclophosphamide. PTCD was accomplished using monoclonal antibody T10B9 or OKT3 and complement. All patients engrafted, with a median time of 18 days to ANC >500. Only one patient had greater than grade II acute GVHD; two patients had limited and one patient extensive chronic GVHD. Nine patients are alive and transfusion independent at a median months post BMT. Three patients died from infection or renal failure. This series suggests that an aggressive immunosuppressive conditioning regimen with PTCD results in successful engraftment and minimal GVHD in pediatric patients with SAA, even with HLA mismatched donors.

Hematopoietic stem cell transplantation for severe aplastic anemia--experience of an institute in Taiwan

Hematopoietic stem cell transplantation (HSCT) is an accepted treatment strategy for patients with severe aplastic anemia (SAA). We report our experience in a general hospital in Taiwan. From March 1985 to July 2001, 79 consecutive SAA patients, 46 male and 33 female, with a median age of 22 (4–43) years, received 80 courses of transplantation. Cyclophosphamide and total body radiation were used for the conditioning regimen, and cyclosporine-A and methotrexate for graft-versus-host disease (GVHD) prevention. Patients were followed for a median of 39 months (from 8 days to 194 months). Myeloid and platelet engraftment occurred in a median of 15 (8–27) days and 18 (8–77) days, respectively. Three patients had primary and three patients secondary graft failure. Five patients (6.8%) had grade II–IV acute GVHD in 73 evaluable patients. Chronic GVHD occurred in 23 (34.8%) patients, with extensive stage in six. Only two patients had CMV disease. The projected 3- and 5-year overall survival rates estimated by the Kaplan-Meier method were 76.08 and 74.13%, respectively. Age at transplant, non-sibling donor, mononuclear cell dose, grade II–IV acute GVHD, interval from diagnosis to transplant, and red blood cell and platelet transfusion before transplant were poor prognostic factors for overall survival by univariate analysis. Grade II–IV acute GVHD was the only prognostic factor affecting overall survival after multivariate Cox regression analysis (P=0.040). In conclusion, SAA patients receiving HSCT have good long-term survival. The low incidence of acute GVHD in our patients may be related to ethnicity.

New approaches to hematopoietic cell transplantation for hematological diseases in children

Hematopoietic cell transplantation (HCT) has been used for more 30 years for the treatment of selected malignant and nonmalignant diseases. Traditionally, HCT for hematological disorders has relied on myeloablative conditioning before HLA-identical sibling bone marrow transplantation to correct the underlying hematological defect. Most children with hematological diseases who are referred to HCT have features that portend significant morbidity and early mortality. Among SAA patients who have HLA-identical sibling donors, younger patients with profound pancytopenia might be considered early for HCT. For others who lack sibling donors, patients who receive HCT from alternate sources have generally failed one or more courses of intensive immunosuppressive therapy and remain transfusion-dependent, some with hemosiderosis, red cell alloimmunization, and platelet transfusion refractoriness [44,46,48]. Currently, HCT for SCD is generally restricted to those who have experienced a significant sickle-related complication such as stroke, recurrent acute chest syndrome, or recurrent painful episodes [7,13]. In contrast, most reserve HCT in thalassemia for younger, Lucarelli class I, good-risk patients who have HLA-identical sibling donors, and veer away from older, high-risk thalassemics for whom transplantation is a riskier clinical intervention. For groups such as young adults with thalassemia major, HCT might become more widely applicable if its toxicity was reduced. Several approaches undergoing development include reduced-intensity conditioning and attempts to prevent GVHD. New methods to reduce the intensity and toxicity of conditioning as well as to use highly purified stem cells with the reduction in graft versus host disease may allow for the use of matched unrelated donors or haploidentical donors. This would serve to provide potentially more children who could benefit from stem cell transplantation with donors. These advances will hopefully lead to benefits for the majority of children who lack HLA-identical donors.

Unrelated donor marrow transplantation in children with severe aplastic anaemia using cyclophosphamide, anti-thymocyte globulin and total body irradiation

We report a favourable outcome in 15 patients with severe aplastic anaemia (SAA) who were < 20 years of age and who underwent bone marrow transplantation (BMT) from a human leucocyte antigen (HLA)-matched unrelated donor. All patients were non-responders to intensive immunosuppressive therapy (IST) and were multiply transfused. The conditioning regimen consisted of cyclophosphamide (60 mg/kg/d, on d -4 and -3), anti-thymocyte globulin (2.5 mg/kg/d, on d -5 to -2) and total body irradiation (2.5 Gy x 2/d, on d -2 and -1). Patients received cyclosporine and methotrexate for prophylaxis of graft-versus-host disease (GVHD), except for the last four who received tacrolimus instead of cyclosporine. Donor/recipient pairs were identical for HLA class I and II antigens by serological typing, but four pairs were found to have a mismatch at the HLA-A, -B or -DRB1 locus by high-resolution typing. All patients achieved rapid engraftment and are alive at 2-86 months after transplantation (median follow-up, 51 months). Moderate to severe acute GVHD occurred in 5 out of 15 patients (33%); only one patient developed extensive chronic GVHD. Considering our encouraging results, unrelated donor transplantation for SAA is recommended as a salvage therapy in non-responders to IST.

Improved outcome of alternative donor bone marrow transplantation in children with severe aplastic anaemia using a conditioning regimen containing low-dose total body irradiation, cyclophosphamide and Campath

The increasing success of human leucocyte antigen (HLA)-matched sibling donor (MSD) transplants and combination immunosuppressive treatments have dramatically improved the prognosis of severe aplastic anaemia (SAA) in children and young adults. For patients who lack a MSD there is a significant minority who fail immunosuppressive therapy or suffer from a severe constitutional aplastic anaemia in which immunosuppression would be ineffective. Alternative donor bone marrow transplantation (AD-BMT) has only had limited success in this context. We report the successful outcome of AD-BMT in eight consecutive patients aged 7 months to 15 years, six of whom had acquired aplastic anaemia who had previously failed to respond to immunosuppression, and two of whom had a severe (non-Fanconi) constitutional aplastic anaemia. All eight patients had received multiple red cell and platelet transfusions. We used a new combination of agents for pretransplant conditioning aiming to maximize immunosuppression and minimize toxicity, consisting of Campath-1G or -1H, cyclophosphamide and low-dose total body irradiation (LD TBI) or fludarabine. Toxicity was minimal and all eight children are alive, well and free of disease at a median follow-up of 32 months. We suggest that this approach could facilitate the successful treatment of children with SAA in whom immunosuppressive therapy has failed or is not appropriate.

Single institution outcomes of treatment of severe aplastic anaemia

BACKGROUND

In severe aplastic anaemia, the treatment of choice for young patients with a human leucocyte antigen-matched sibling is now established as allogeneic bone marrow transplantation (BMT). In older patients and in those without a matched sibling donor, immunosuppressive therapy is the usual first option. 'Alternative' marrow donors are emerging as an option for those without a matched sibling donor.

AIMS

To review 10 years of local experience in treating severe aplastic anaemia with BMT and immunosuppressive therapy with emphasis on long-term outcomes.

METHODS

A retrospective analysis was performed of all patients with severe aplastic anaemia presenting to the Royal Brisbane and Royal Children's Hospitals between 1989 and 1999. Data were abstracted regarding patient demographics, pretreatment characteristics and outcome measures, including response rates, overall survival and long-term complications.

RESULTS

Twenty-seven consecutive patients were identified, 12 treated with immunosuppression alone and 15 with BMT. In these two groups, transfusion independence was attained in 25% and 100%, respectively, with overall survival being 36% and 100%, respectively. Those treated with immunosuppression were significantly older (median 41.5 versus 22 years, P = 0.008). Long-term survivors of either treatment had extremely low morbidity. Three patients carried pregnancies to term post-transplant. Three patients received alternative donor BMT with correspondingly excellent survival.

CONCLUSIONS

Patients treated with allogeneic BMT for severe aplastic anaemia enjoyed extremely good long-term survival and minimal morbidity. Patients treated with immunosuppressive therapy had a poorer outcome reflecting their older age and different usage of therapies over the past decade. Optimal treatment strategies for severe aplastic anaemia remain to be determined.

Unrelated donor hematopoietic transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for a range of malignant and non-malignant diseases. Unfortunately, fewer than 30% of patients have a human leukocyte antigen (HLA)-matched sibling. Advances in our understanding of the HLA system and the development of large international donor registries are supporting the increasing use of unrelated donors as an alternative source of stem cells. Unrelated donor transplantation, however, is still associated with higher complication rates than in HLA-identical sibling donor transplants. Improvements in graft-vs.-host disease prevention and treatment, new conditioning regimens and better donor selection will likely expand the indications of unrelated donor HSCT in the next decade.

A fludarabine-based conditioning regimen for severe aplastic anemia

Graft rejection is a common problem after alternative donor transplantation for patients with refractory severe aplastic anemia (SAA). Intensification of the conditioning regimen, with the inclusion of irradiation, has often been advocated to combat this problem. With this approach engraftment rate improved, but the incidence of transplant-related complications is also increased, resulting in little change in the overall outcome. We investigated the use of the combination of fludarabine, cyclophosphamide and anti-thymocyte globulin as the conditioning regimen in five multiply-transfused SAA patients. Three patients received an HLA one-antigen disparate related donor transplant, while two patients were given marrow from matched, unrelated donors. The regimen was well tolerated, with only grade I toxicity encountered. With a median follow-up of 9 months, all patients are alive with complete donor chimerism. We conclude that fludarabine may be used in place of irradiation to augment the conditioning regimen of cyclophosphamide and anti-thymocyte globulin for alternative donor transplantation in children with SAA.

Aplastic anaemia: management

Acquired, idiosyncratic aplastic anaemia (AA) is a rare but potentially fatal haematological disorder. Severe AA constitutes an acute medical emergency, and supportive therapy is needed to prevent overwhelming sepsis or a life threatening haemorrhage. Specific therapy for the disease includes the choice between allogeneic stem cell transplantation (SCT) from an HLA-identical sibling or immunosuppressive therapy with anti-thymocyte globulin (ATG) and cyclosporin A (CSA). Long-term cure rates of 75-90% are now achieved following HLA (human leukocyte antigen) identical sibling bone marrow transplant. The use of donors other than HLA-id siblings for transplantation in AA remains experimental. Transplantation offers the patient a chance of cure, whilst treatment with immunosuppressive therapy carries a long-term risk of relapse and clonal transformation. The haemopoietic growth factors, apart from granulocyte colony stimulating factor (G-CSF), have been shown to be potentially toxic when given to patients with AA. A short course of G-CSF may be useful to help treat severe infection, but its longer-term use with ATG and CSA remains controversial. Results from immunosuppressive treatment continue to improve with time, as a result of the additional use of CSA with ATG, the use of repeat courses of ATG for non-responders and improvements in the supportive care of patients.

Alternative-donor hematopoietic stem-cell transplantation for severe aplastic anemia

Bone marrow transplantation (BMT) from a human leukocyte antigen (HLA)-matched sibling is the treatment of choice in children and young adults with severe aplastic anemia (SAA). However, because only 30% of patients have a suitable donor, more aggressive nontransplant immunosuppressive regimens have been used, with reasonable results. The use of mismatched family member and unrelated donors, initially fraught with problems of nonengraftment and severe graft-versus-host disease (GVHD), has improved markedly over the past 10 years. The establishment of donor registries, more precise HLA typing methods, and better supportive care are significant factors in the improved outcomes. The challenge for the future is to assemble the optimal combination of donor selection, conditioning regimen, and GVHD prophylaxis to enhance disease-free survival. These better outcomes should encourage the treating physician to consider stem-cell transplant at an earlier stage of disease.

Allogeneic hematopoietic stem-cell engraftment and graft failure

Two immunologically mediated reactions, the graft-versus-host (GvH) and host-versus-graft (HvG) responses, form primary and opposing barriers to successful transplantation of allogeneic hematopoietic stem-cells (HSC). The HvG barrier is set by the strength of the allogeneic immune response, which is determined by antigenic stimulation provided by donor cells, owing to differences in histocompatibility antigens, and the capacity of host immune cells to generate a response. Risk of graft failure must be viewed as the interplay of multiple factors, including degree of human leukocyte antigen and minor histocompatibility antigen disparity, capacity of host immune response, and the capacity of donor hematopoietic and immunologic cells for overcoming residual host immunity.

Practical aspects in the diagnosis and management of aplastic anemia

Aplastic anemia may result from several pathogenic mechanisms, the most common is idiopathic. The current definitive treatments for aplastic anemia are bone marrow transplantation (BMT) or immunosuppressive (IS) therapy. The benefits of each are comparable. However, certain subsets of patients derive superior benefit from one or the other. Bone marrow transplantation is the initial treatment of choice for young patients (< 20 years old). It results in the complete reconstitution of hematopoiesis, whereas autologous hematopoietic remissions after IS therapy are more susceptible to relapse. Survival rates after BMT, in patients between the ages of 20 and 40, are comparable to those reported for IS therapy. Better survival rates after BMT have been achieved with improved conditioning regimens and graft-versus-host disease prophylaxis. For patients older than 40, the treatment of choice is IS. Long-term complications of IS therapy include recurrence and development of clonal myeloid disorders. Long-term complications after BMT include graft-versus-host disease and secondary neoplasms. The IS regimen includes the combination of antithymocyte globulin and cyclosporin A. The addition of growth factor to the IS regimen seems promising; however, their use on their own is not recommended. Androgens have been shown to be inferior in the treatment of aplastic anemia. The role of BMT from an unrelated donor is being investigated.