Non-Myeloablative Allogeneic Hematopoietic Transplantation in Relapsed/Primary Refractory Follicular Lymphoma.

Allogeneic stem cell transplantation (SCT) can induce long-term disease-free survival in refractory follicular lymphomas (FL) but is impaired by high rate of transplant-related mortality (TRM). Reduced conditioning followed by allogeneic SCT is a promising concept in FL, allowing a graft-versus-lymphoma (GVL) effect while reducing the TRM. We piloted a clinical trial using this approach in relapsed/primary refractory low-grade lymphomas. From 1998 to 2003, 31 patients (pts) with an HLA-identical sibling have been enrolled. Main pts characteristics were : age = 49 years (range, 32–61 y); grade : I/II FL = 26; FL with histologic transformation = 5; gender = 16 male and 15 female; ≥ 2 prior therapies before transplantation = 23; primary refractory = 8; stage IV = 22; Bulky disease = 16; mean LDH rate before transplantation = 335 UI/l (range, 205–858); residual disease at transplantation (partial response (PR) + progression) = 20. Previous treatments were as follow : anthracyclins = 26, alkylants = 21, anti-CD20 = 15, purine analogs = 7, autologous SCT = 6, radiotherapy = 5. The conditioning regimen was IV fludarabine 30 mg/m²/day (from day −5 to −2); PO busulfan 2 mg/kg/day (from day −7 to −6); antithymocyte globulin (ATG) 2.5 mg/kg/day (from day −4 to −3). 14/31 (45%) and 17/31 (55%) pts received peripheral blood and bone marrow stem cells respectively with a median number of CD34⁺ cells of 5 x 10⁶/kg (range, 1.8–11.9). Graft-versus-host-disease (GVHD) prophylaxis consisted in cyclosporine A alone. All patients achieved complete donor (> 95%) chimerism after allogeneic SCT. Median duration of neutropenia (< 0.5 G/L) and thrombocytopenia (< 25 G/L) were 3 days (range, 0–16) and 3 days (range, 0–29) respectively. 8/31 pts (26%) had CMV reactivation but no CMV disease. 3/31 (10%) developed grade II–IV acute GVHD. 10/31 (32%) developed chronic GVHD (5 moderate and 5 extensive). The median follow-up time was 20 months. The TRM was 19% (6/31). Causes of death were aGVHD = 1, auto-immune hepatitis = 1, bacteraemia = 2, pulmonary toxoplasmosis = 1 and Lyell syndrome = 1. Overall response rate was 97% (21 CR + 9 PR) at day 100 and at 1 year (24 CR + 6 PR). The estimated 2-year overall survival (OS), event-free survival (EFS) and relapse-free survival (RFS) rate were 75%, 65% and 85% respectively. 2 relapses occurred. Both were treated by anti-CD20, achieved CR and are still alive. Donor age, Bulky disease and LDH were significant for EFS. Altogether, these data suggest that non-myeloablative SCT can induce a high rate of durable remissions with reduced toxicity in this poor risk population.