Upfront Haploidentical Stem Cell Transplant With Posttransplant Cyclophosphamide in Children With Severe Aplastic Anemia

Haploidentical Hematopoietic Stem Cell Transplantation in Pediatric Patients with Acquired Hypocellular Bone Marrow Failure

Children with acquired hypocellular bone marrow failure of unknown cause (AHBMF) are usually diagnosed either with severe aplastic anemia (SAA) or refractory cytopenia of childhood (RCC). Patients with AHBMF who lack a matched donor and who failed or relapsed after immunosuppressive therapy (IST) need alternative therapies. Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) offers a curative treatment for these patients. We report a multicenter Spanish experience with haplo-HSCT in pediatric patients with AHBMF. Eleven pediatric patients (SAA, n = 9; RCC, n = 2) underwent haplo-HSCT with different lymphodepletion strategies. Most patients (10 of 11) had previously failed to respond or relapsed after IST. The conditioning regimen was reduced intensity in SAA and myeloablative in RCC. Patients with SAA received low-dose radiotherapy as part of their conditioning regimen. All patients engrafted. Viral reactivation was common (8 of 11). Acute GVHD grade ≥II was seen in 5 patients. Chronic GVHD was diagnosed in 4 of the long-term survivors. Transplantation-associated microangiopathy was a frequent complication in SAA patients and was related to worse outcome. Two patients died of transplantation-related complications. Overall survival was 81%, with a median follow-up of 36 months. Haplo-HSCT can be a successful salvage curative treatment for pediatric patients with AHBMF, but with significant toxicities that must be addressed. Transplantation-associated microangiopathy was the most critical complication.

Impact of Conditioning Regimen and Graft-versus-Host Disease Prophylaxis on The Outcome of Haploidentical Peripheral Blood Stem Cell Transplantation for High-Risk Severe Aplastic Anemia in Children and Young Adults: A Report from the Pediatric Severe Aplastic Anemia Consortium of India

Allogenic hematopoietic cell transplantation (HCT) is the best curative approach for patients with severe aplastic anemia (SAA). The outcomes of HCT from haploidentical family donors (HFDs) have improved, making it a feasible option for patients lacking an HLA-identical donor. However, data on HFD-HCT for younger patients with SAA is sparse. In this multicenter retrospective study, we evaluated the outcomes of 79 patients undergoing HFD-HCT for SAA. All the patients were heavily pretransfused, the median time to HCT was >12 months, and 67% had failed previous therapies. Conditioning was based on fludarabine (Flu)-cyclophosphamide (Cy)-antithymocyte globulin (ATG)/total body irradiation (TBI) with or without thiotepa/melphalan (TT/Mel). Post-transplantation Cy (PTCy) and calcineurin inhibitors (CNIs)/sirolimus were used as graft-versus-host disease (GVHD) prophylaxis with or without abatacept. The rate of primary graft failure (PGF) was 16.43% overall, lower in patients conditioned with TT/Mel. The incidences of acute and chronic GVHD were 26.4% and 18.9%, respectively. At a median follow-up of 48 months, the overall survival (OS) and event-free survival (EFS) were 61.6% and 58.1%, respectively. Both OS and EFS were better in the TT/Mel recipients and with abatacept as GVHD prophylaxis. On multivariate analysis, the use of abatacept was found to favorably impact the outcome variables, including GVHD and EFS. Our study suggests that PTCy-based HFD-HCT is a reasonable option for young patients with high-risk SAA, in whom optimization of conditioning and GVHD prophylaxis might further improve outcomes.

Alternative Transplantation With Post-Transplantation Cyclophosphamide in Aplastic Anemia: A Retrospective Report From the BMF-WG of Hunan Province, China

Although the possibility of first-line hematopoietic cell transplantation (HCT) from alternative donors in severe aplastic anemia (SAA) patients has been suggested recently, transplantation strategies are still being investigated. We established a novel post-transplantation cyclophosphamide-based HCT protocol for patients with SAA in prior studies. We explores the effectiveness and safety of this HCT approach either as first-line or as salvage treatment in SAA patients. Outcomes of 71 consecutive young patients, who received HCT from unrelated or haploidentical donors, were retrospectively analyzed. According to their treatment before transplantation, the patients were classified into treatment-naive (TN) and relapsed or refractory (R/R) patients. The R/R patients were designated as such when a patient did not respond to previous immunosuppressive therapy or relapsed. We administered an antithymocyte globulin (ATG)-free, total body irradiation (TBI)-free conditioning regimen comprising cyclophosphamide, busulfan, and fludarabine, all in an intravenous formula. We used a thorough post-transplantation prophylaxis regimen for GVHD, including post-transplantation cyclophosphamide (PTCy) and short-term methotrexate and long-term cyclosporine A. The median age of the cohort was 16 (95% confidence interval, 12-20) years at transplantation. Most patients (61 of 71) received HCT from haploidentical donors, and the others received HCT from unrelated donors. TN patients (n = 38) were younger and had a shorter time-to-transplant and lower HCT-specific comorbidity index than patients with R/R diseases (n = 33). The frequencies of graft failure, grade II-IV acute graft-versus-host disease (GVHD), and moderate-severe chronic GVHD were similar, at 5.3% versus 6.5% (P = .057), 8.3% versus 0% (P = .109), and 5.7% versus 0% (P = .199) between R/R and TN patients. With a median 42-month follow-up, the frequencies of overall survival (OS) and event-free survival (EFS) were higher in the TN group than in the R/R group (100% versus 84.8% [P = .013] and 86.8% versus 75.8% [P = .255], respectively). All patients who achieved successful engraftment showed full donor chimerism. Four patients, all in the R/R group, suffered from donor-type aplasia; of these, 2 died, 1 was salvaged with another transplantation, and the final one was still receiving transfusion at the last follow-up. Currently, 93.9% (62 of 66) of the patients are alive more than 12 months after transplantation; of these 93.5% (58 of 62) no longer receive immunosuppression, including 91.7% (33 of 34) of the TN group and 89.3% (25 of 28) in the R/R group. This novel TBI-free and ATG-free HCT protocol using a reduced-intensity conditioning regimen followed by modified PTCy achieved promising engraftment, minimal GVHD risk, and encouraging OS and EFS. Our study suggests that unrelated or haploidentical HCT with PTCy can be used as a first-line treatment for young patients with SAA. Nevertheless, further efforts are needed to explore possibilities for older patients and patients with a poor performance status.