Reduced-Intensity Conditioning with Fludarabine, Cyclophosphamide, and High-Dose Rituximab for Allogeneic Hematopoietic Cell Transplantation for Follicular Lymphoma: A Phase Two Multicenter Trial from the Blood and Marrow Transplant Clinical Trials Network

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Allogeneic hematopoietic cell transplantation (alloHCT) can induce long term remissions in chemosensitive relapsed follicular lymphoma (FL). The BMT CTN conducted a multicenter phase 2 trial to examine the efficacy of alloHCT using reduced intensity conditioning (RIC) with rituximab (RTX) in multiply relapsed, chemosensitive FL. The primary endpoint was 2 year progression-free survival (PFS). The conditioning regimen consisted of fludarabine, cyclophosphamide and high-dose RTX (FCR) in which 3 of the 4 doses of RTX were administered at a dose of 1 gm/m2. Graft vs host disease (GvHD) prophylaxis was with tacrolimus and methotrexate. Sixty five patients were enrolled and 62 were evaluable. Median age was 55 years (range, 29-74). This group was heavily pre-treated: 77% had received ≥ 3 prior regimens, 32% had received ≥ 5 prior regimens and 11% had received prior autologous HCT. Donors were HLA-matched siblings (n=33) or HLA-matched unrelated adults (n=29). No graft failures occurred. The overall response rate after HCT was 94% with 90% in complete remission (CR), including 24 patients not in CR before alloHCT. With a median follow-up of 47 months (range, 30-73), 3 year PFS and overall survival rates were 71% (95% confidence interval: 58%-81%) and 82% (70%-90%) respectively. Three year cumulative incidences of relapse/progression and non-relapse mortality were 13% and 16%, respectively. Two year cumulative incidences of grade 2-4 and grade 3-4 acute GvHD were 27% and 10%, respectively and extensive chronic GvHD incidence was 55%. Serum RTX concentrations peaked at day +28 and remained detectable as late as 1 year in 59% of patients with available data. In conclusion, alloHCT with FCR conditioning confers high CR rates, a low incidence of relapse/progression and excellent survival probabilities in heavily pretreated FL patients.

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