Rituximab, fludarabine, and total body irradiation as conditioning regimen before allogeneic hematopoietic stem cell transplantation for advanced chronic lymphocytic leukemia: long-term prospective multicenter study.

To evaluate the efficacy and toxicity of reduced-intensity conditioning (RIC) combining fludarabine, low-dose total body irradiation (TBI) and rituximab before allogeneic hematopoietic stem cell transplantation (allo-HSCT) from human leucocyte antigen (HLA) identical siblings, we conducted a prospective study in patients ≤65 years old with advanced chronic lymphocytic leukemia (CLL) stage B or C in response after a salvage treatment. Conditioning included rituximab (375 mg/m² on day 5), fludarabine (30 mg/m² from day 4 to day 2), TBI (2 Gy on day 0), and rituximab (500 mg/m² on days 1 and 8). Forty patients were included, 34 (85%) were male with a median age of 54 years (range, 35-65 years), 38 (95%) were in B stage, and 2 were in stage C; only 7 patients (17%) were in complete response. Seven (17%) patients did not receive rituximab. Thirty-nine (98%) patients engrafted, 17 patients developed acute graft-versus-host disease (GVHD) grade ≥II with a cumulative incidence at 3 months of 44% (36-52) with a significant protective effect of rituximab (p = 0.02). The cumulative incidence of chronic GVHD was 29% (21-36) at 12 months for both limited and extensive forms. The median overall survival was not reached with 5-years probability of 55% (41-74). The multivariate analysis showed a positive effect of rituximab on overall survival and event-free survival (hazard ratio [HR] = 0.1 [0-0.6], p = 0.02; and HR = 0.1 [0-0.4], p = 0.035, respectively). The association of fludarabine, TBI, and rituximab is feasible, well tolerated, and allows better outcomes in advanced CLL.