Uniform Graft-versus-Host Disease Prophylaxis using Post-Transplantation Cyclophosphamide, Methotrexate, and Cyclosporine following Peripheral Blood Hematopoietic Stem Cell Transplantation from Matched and Haploidentical Donors for Transfusion-Dependent Thalassemia: A Retrospective Report from the Bone Marrow Failure Working Group of Hunan Province, China.

Although the survival of patients with transfusion-dependent thalassemia (TD-TM) is reportedly inferior after haploidentical hematopoietic stem cell transplantation (HSCT), the heterogeneity of transplantation approaches in studies suggests the need to assess the effect of conditioning regimen on matched and haploidentical transplantation outcomes. A novel post-transplantation cyclophosphamide (PTCy)-based approach for patients with TD-TM undergoing haploidentical HSCT was reported in our prior study. Here we aimed to retrospectively evaluate the real-world efficacy and safety of graft-versus-host disease (GVHD) prophylaxis in patients with TD-TM after HSCT from matched donors and haploidentical donors (HIDs). In this retrospective multicenter study, among 238 patients with TD-TM who underwent HSCT, 160 underwent peripheral blood HSCT, using uniform GVHD prophylaxis with PTCy, methotrexate, and cyclosporine, at member centers of the Bone Marrow Failure Working Group of Hunan Province between 2019 and 2023. The median age of the cohort at transplantation was 6 years (95% confidence interval [CI], 6 to 7 years). The 160 donors included 99 (61.9%) haploidentical family members, 13 matched sibling donors, and 48 matched or mismatched unrelated donors. The engraftment rate was 98.8% (95% CI, 96.1% to 97.7%). HSCT from HIDs had a lower risk of mixed chimerism (HR, .078; P = .022). Within 100 days after transplantation, 31 patients (19.6%; 95% CI, 14.0% to 26.3%) had grade II-IV acute GVHD (aGVHD), 9 of whom had grade III-IV aGVHD (5.7%; 95% CI, 2.9% to 10.1%). HIDs were significantly associated with a higher risk of grade II-IV aGVHD (HR, 3.973; P = .009). Nineteen patients (11.9%; 95% CI, 7.6% to 17.6%) developed late aGVHD after a median of 516 days (95% CI, 407 to 709 days). Twenty-six patients (16.5%; 95% CI, 11.3% to 22.8%) exhibited any 1 of the diagnostic, distinctive, or atypical features of chronic GVHD (cGVHD) according to the 2014 National Institutes of Health (NIH) criteria after a median of 690 days (95% CI, 496 to 902 days). Among these 26 patients, 7 had NIH-defined cGVHD, 14 had only 1 distinctive sign with no histologic evidence, and 5 had only atypical cGVHD signs. Of the 26 patients, 5 were classified with overlap syndrome. Of 21 patients classified with NIH-defined and potential cGVHD, 3 had moderate cGVHD and 1 had severe cGVHD. Logistic regression analyses identified that grade II-IV aGVHD independently predicted subsequent cGVHD (HR, 3.920; P = .006). The rates of cGVHD were similar in the matched donor and HID groups. Thalassemia-free survival (TFS) and event-free survival (EFS) were 97.5% (95% CI, 94.2% to 99.2%) and 90.6% (95% CI, 85.4% to 94.4%), respectively, after a median of 690 days (95% CI, 496 to 902 days). TFS rates were similar in the matched donor and HID groups (P = .549). The EFS rate was significantly higher in the matched donor group compared to the HID group (P = .033). Our study suggests that when PTCy-based uniform GVHD prophylaxis is administered, HSCT from matched donors and HIDs results in a low incidence of severe GVHD and treatment-related mortality with satisfactory survival.