Peripheral blood versus bone marrow transplant in patients with aplastic anemia, an unresolved issue

Outcome of peripheral blood stem cell transplantation from HLA-identical sibling donors for adult patients with aplastic anemia

Although bone marrow transplantation is the recommended form of allogeneic hematopoietic stem cell transplantation for aplastic anemia, some patients undergo peripheral blood stem cell transplantation (PBSCT). Therefore, there is critical demand to identify factors affecting transplantation outcomes. Using the Japanese registry database, we retrospectively analyzed outcomes of 94 adult patients with aplastic anemia who underwent PBSCT from HLA-identical sibling donors. The cumulative incidence of neutrophil engraftment was 94% (95% confidence interval [CI] 86-97%), and was significantly higher in patients who received anti-thymocyte globulin (ATG) in conditioning. The cumulative incidence rate was 26% (95% CI 17-35%) in grades II-IV acute graft-versus-host disease (GVHD) and 20% (95% CI 13-29%) in extensive chronic GVHD, and tended to be lower in patients with chronic GVHD who received ATG-based conditioning. The 5-year overall survival (OS) rate was 70% (95% CI 59-78%). In multivariate analysis, patient age < 40 years, shorter period from diagnosis to transplantation, better performance status, and ATG-based conditioning were significantly correlated with favorable OS. In conclusion, PBSCT from HLA-identical sibling donors for aplastic anemia would result in acceptable outcomes. Several risk factors identified in our study should be considered when selecting a stem cell source.

High Failure-Free Survival after Unrelated Donor Peripheral Blood Stem Cell Transplantation in Pediatric Severe Aplastic Anemia

The use of alternative donor peripheral blood stem cell transplantation (PBSCT) has increased in recent years. In this study, we analyzed the effect of stem cell source and HLA disparity on outcomes in pediatric patients with severe aplastic anemia (SAA). A total of 134 patients who underwent HSCT with nonmyeloablative conditioning between 2006 and 2020 were enrolled and classified into 3 groups: HLA-matched bone marrow transplantation (M-BMT; n = 24), HLA-matched PBSCT (M-PBSCT; n = 66), and HLA-mismatched PBSCT (MM-PBSCT; n = 44). Significantly higher stem cell doses were obtained for PBSCT than for BMT. A total of 13 patients experienced secondary graft failure (GF), with a cumulative incidence (CI) of 10.0%. HLA-mismatched PBSCT and a very severe degree of disease significantly decreased the incidence of secondary GF. The CI of grade II-IV acute graft-versus-host disease (GVHD) was significantly higher in PBSCT than in BMT, but the CI of grade III-IV acute GVHD and CI of chronic GVHD requiring systemic treatment did not increase in PBSCT. The estimated 5-year overall survival (OS), failure-free survival (FFS), and GVHD-free failure-free survival (GFFS) of the total cohort were 93.0%, 89.5%, and 77.5%, respectively. The most favorable FFS was observed in the MM-PBSCT group (97.6%; P = .03), whereas OS and GFFS were similar across the 3 groups. In multivariate analysis, HLA mismatch and short time from diagnosis to transplantation were associated with superior FFS. Unrelated donor PBSCT with low-intensity SAA conditioning showed favorable outcomes in terms of low rate of secondary GF, higher FFS, and manageable GVHD regardless of HLA compatibility. Our findings suggest the feasibility of PBSCT from unrelated donors, resulting in the possible expansion of the donor pool in transplantation for pediatric SAA. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Transplant in Aplastic Anemia Using Combined Granulocyte Colony-Stimulating Factor Primed Blood and Bone Marrow Stem Cells: A Retrospective Analysis

INTRODUCTION

Aplastic anemia (AA) is characterized by diminished hematopoietic precursors in the bone marrow, most often due to injury to the pluripotent stem cell. In Pakistan, AA is not uncommon, and allogeneic hematopoietic stem cell transplant remains the only curative option for these patients.

OBJECTIVE

The objective of this study was to determine the transplant outcome of combined granulocyte colony-stimulating factor (G-CSF) primed blood and bone marrow grafts in adult and pediatric patients with AA.

METHODS

We retrospectively collected the data of all transplant procedures performed from 2004 to 2019 at Aga Khan University in Karachi, Pakistan. Variables analyzed included age, sex, type of stem cells used, conditioning regimens, and overall survival for patients undergoing transplant in AA.

RESULTS

A total of 351 transplants were performed during the study period. Out of these, 239 were allogeneic transplants, whereas 112 were autologous procedures. We performed 70 transplants for AA during the study period, of which 52 were male patients and 18 were female patients. The median age ± standard deviation (SD) was 17.5 ± 9.4 years (range, 2-43 years). Cyclophosphamide/antithymocyte globulin (ATG) was used as a conditioning regimen in 65 patients, while ATG/cyclophosphamide/fludarabine was used in 5 patients. In 60 patients, a combination of G-CSF primed blood and bone marrow stem cells were used. The mean CD34 count was 5.2 × 10⁶/kg. Graft-vs-host disease (GVHD) prophylaxis was done with cyclosporine and methotrexate. All patients received standard infection prophylaxis. Engraftment was achieved in 86% of patients. The median day of myeloid engraftment was 15 (range, 10-22 days). Chronic GVHD was present in 3 patients while 4 had acute GVHD. The overall survival was 71.2% (median duration of 80 months). The main cause of mortality was gram-negative sepsis.

CONCLUSION

A combination of blood and bone marrow stem cells results in early engraftment with decreased frequency of GVHD in AA. The overall survival was comparable to international literature.

Aplastic Anemia Preconditioned with Fludarabine, Cyclophosphamide, and Anti-Thymocyte Globulin

Background

Graft rejection and graft versus host disease (GvHD) have impeded the success of hematopoietic cell transplantation for severe aplastic anemia (SAA) patients. There is no sufficient data to identify the outcomes of peripheral blood stem cell transplantation (PBSCT) in SAA patients, especially for adult SAA patients. The aim of this study was to evaluate the outcomes of adult SAA patients undergoing PBSCT with the FCA regimen. The FCA regimen includes fludarabine, cyclophosphamide, and anti-thymocyte globulin (ATG).

Material/Methods

We report our experience with 46 adult SAA patients who underwent PBSCT with the FCA regimen. Thirty SAA patients who received only cyclophosphamide and ATG (CA) regimen were used as controls. Complications and survival outcomes were evaluated and compared.

Results

There was a significantly higher percentage of patients who achieved >95% donor chimerism by day 30 in the FCA group. The 5-year event-free survival (EFS) rate in the FCA group was higher than that in the CA group (95.4% versus 73.3%). In addition, the 5-year rejection rate (RR) in the FCA group was lower than that in the CA group (4.6% versus 23.6%). A multivariable model identified the FCA regimen as an independent factor affecting EFS and RR. However, GvHD and serious infection did not differ between the 2 groups. For patients with an unrelated donor, the FCA regimen had a higher EFS and a lower RR than the CA regimen.

Conclusions

The FCA regimen for PBSCT in adult SAA patients compared favorably to the CA regimen. It can improve EFS and reduce graft rejection, especially for unrelated donor PBSCT.

Hematopoietic cell transplantation for aplastic anemia

PURPOSE OF REVIEW

Improvements in allogeneic hematopoietic cell transplantation (HCT) with better donor selection, conditioning regimens and graft vs. host disease prophylaxis make it reasonable to move HCT earlier in the algorithm for management of severe aplastic anemia (SAA). Recent progress in transplantation is reviewed whereas issues related to developing countries are also addressed.

RECENT FINDINGS

Multiple research centers are reporting on clonality, mutations and telomere disorders in SAA, which may help to choose the most appropriate therapy upfront. Eltrombopag, in combination with immunosuppressive therapy (IST), has shown remarkable improvement over historical IST, and long-term follow-up is awaited. In younger patients and in experienced centers, matched unrelated-donor (MUD) and related haploidentical transplants (haplo-HCT) are being reported with survival approaching that seen with sibling transplants. Literature from resource-limited countries highlight the need to modify guidelines to make them affordable and cost-effective. Bone marrow remains the graft source of choice; peripheral blood stem cells may be acceptable in special circumstances in resource-constrained countries.

SUMMARY

The potential of novel research findings and new therapeutic trials should be maximized by validation in different centers, countries and patient populations to provide personalized care to patients with aplastic anemia.