Patients often undergo consolidation allogeneic hematopoietic stem cell transplantation (allo-HSCT) to maintain long-term remission following chimeric antigen receptor (CAR) T-cell therapy. Comparisons of safety and efficacy of allo-HSCT following complete remission (CR) achieved by CAR-T therapy versus by chemotherapy for B-cell acute lymphoblastic leukemia (B-ALL) has not been reported. We performed a parallel comparison of transplant outcomes in 105 consecutive B-ALL patients who received allo-HSCT after achieving CR with CAR-T therapy (n=27) or with chemotherapy (n=78). The CAR-T-allo-HSCT group had more patients in second CR compared to the chemotherapy-allo-HSCT group (78% vs. 37%; p<0.01) and more with complex cytogenetics (44% vs. 6%; p<0.001) but the proportion of patients with pre-transplant minimal residual disease (MRD) was similar. The median follow-up time was 49 months (range: 25-54 months). The CAR-T cohort had a higher incidence of Grade II-IV acute graft-versus-host disease (aGVHD 48.1% [95% CI: 46.1-50.1%] vs. 25.6% [95%CI: 25.2-26.0%]; p=0.016). The incidence of Grade III-IV aGVHD was similar in both groups (11.1% vs.11.5%, p=0.945). The overall incidence of chronic GVHD in the CAR-T group was higher compared to the chemotherapy group (73.3% [95%CI: 71.3-75.3%] vs. 55.0% [95%CI: 54.2-55.8%], p=0.107), but the rate of extensive chronic GVHD was similar (11.1% vs.11.9%, p=0.964). Efficacy measures 4 years following transplant were all similar in the CAR-T vs. the chemotherapy groups: cumulative incidences of relapse (CIR; 11.1% vs.12.8%; p=0.84), cumulative incidences of non-relapse mortality (NRM; 18.7% vs. 23.1%; p=0.641) leukemia-free survival (LFS; 70.2% vs. 64.1%; p=0.63) and overall survival (OS; 70.2% vs. 65.4%; p=0.681). We found that pre-transplant MRD-negative CR predicted a lower CIR and a higher LFS compared with MRD-positive CR. In conclusion, our data indicate that, in B-ALL patients, similar clinical safety outcomes could be achieved with either CD19 CAR T-cell therapy followed by allo-HSCT or chemotherapy followed by allo-HSCT. Despite the inclusion of more patients with advanced diseases in the CAR-T group, the 4-year LFS and OS achieved with CAR T-cells followed by allo-HSCT were as remarkable as those achieved with chemotherapy followed by allo-HSCT. Further confirmation of these results requires larger, randomized clinical trials.
Salvage haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is considered in patients with severe aplastic anemia (SAA) if a matched unrelated donor (MUD) is unavailable. However, studies on haplo- and MUD transplantation in SAA are lacking. The present study retrospectively analyzed the outcomes of 89 young SAA patients who underwent unmanipulated alternative HSCT between September 2012 and September 2016 at our single center. Forty-one patients received haploidentical donors and forty-eight patients MUDs for HSCT. Most were heavily transfused and refractory to previous immunotherapy. The median durations for myeloid engraftment in the haplo- and MUD cohorts were 14 (range, 10 to 21) and 13 (range, 10 to 18) days, respectively. Compared with the MUD cohort, haplo-HSCT cohorts had an increased cumulative incidence of acute graft-versus-host disease (GVHD) grades II to IV (43.9% ± 7.8% versus 12.5% ± 4.8%, P = .001) and grades III to IV (21.1% ± 6.7% versus 6.6% ± 3.7%, P = .045) and similar limited chronic GVHD (47.7% ± 8.5% versus 38.5% ± 7.3%, P = .129) and extensive chronic GVHD (12.1% ± 6.8% versus 9.1% ± 4.3%, P = .198). The median follow-up time of the surviving patients was 26 months (range, 6 to 45). No significant differences were observed between haplo-HSCT and MUD HSCT cohorts in 3-year overall survival (80.3% ± 5.1% versus 89.6% ± 7.0%, P = .210), disease-free survival (76.4% ± 5.1% versus 89.4% ± 7.7%, P = .127), and GVHD-free failure-free survival (79.0% ± 8.6% versus 71.6% ± 9.3%, P = .976). Thus, haplo-HSCT, as salvage therapy, achieved similar outcomes as MUD HSCT in young SAA patients, thereby rendering it as an effective and safe option for SAA.
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