Outcomes after Allogeneic Transplantation with Reduced Intensity Conditioning and Post Transplant Cyclophosphamide GvHD Prophylaxis in T-Cell Lymphomas: A Single Institution Experience

Allogeneic stem cell transplantation (allo-SCT) remains a potentially curative treatment for relapsed/refractory aggressive T-cell lymphomas via conditioning chemo- or chemoradiotherapy and graft-versus-lymphoma (GVL) effect. Reduced-intensity conditioning (RIC) regimens with posttransplant cyclophosphamide (PTCy) immunosuppression may improve outcomes by increasing donor availability, reducing treatment toxicity, and shortening the time to immune reconstitution. We report outcomes following RIC and PTCy with an emphasis on Haplo-identical transplantation. This retrospective study enrolled 28 patients with T-ALL:1, ALCL: 6, HSL:1, MF:5, PTCL NOS: 7, and T-PLL: 4 who received allo-SCT from 2019 to 2024 with RIC (Pento/TBI: 20, Flu/Cy/TBI: 7, Flu/TBI: 1). At the time of allo-SCT, 21 patients were in CR and seven were non-CR. All patients received tacrolimus-based GVHD prophylaxis, and 11 received PTCy (50mg/kg day +3 and +4). Outcomes included grade 3-4 acute graft-versus-host disease (aGVHD), extensive chronic GVHD (cGVHD), relapse, non-relapse mortality (NRM), overall survival (OS), relapse-free (RFS), and GVHD-free, relapse-free survival (GRFS). Among the 28 patients, the median age was 61 (range 28-77), and eight were 65 or older. Seventeen (61%) were men. Donors included matched related (MRD) in 2 (7%), matched unrelated (MUD) in 15 (54%), Haplo-identical (Haplo) in 7 (25%), and mismatched unrelated (MMUD) in 4 (14%). Ten (36%) patients had received a prior autologous SCT. The median follow-up after allo-SCT was 11 months (95% CI 4 – 38), and the median OS was not reached. The cumulative incidence rate of aGVHD was 29% and 14% for extensive cGVHD. Overall survival was significantly better for Haplo than MRD/MUD transplantation (median OS not reached vs. 10m; p = 0.015). There was a trend toward longer RFS and fewer relapses with Haplo transplant. By day 100, 16 (57%) patients experienced one or more infections, including bacterial (12), viral (5), and fungal (1). Renal toxicity was noted in 9 (32%) patients. Three (17%) patients had CMV reactivation. Within the first year, 29% (8) of deaths were due to relapse (2), acute GVHD (2), and infection (4). This single-center experience suggests that RIC with PTCy is well-tolerated and associated with improved overall survival. Multi-center studies are needed to evaluate RIC with PTCy prospectively to better define outcomes and potential survival benefits for T-cell lymphoma patients.