NCRI CLL201 Trial: A Randomized Phase II Trial of Fludarabine, Cyclophosphamide and Mitoxantrone (FCM) with or without Rituximab in Previously Treated CLL.

Standard front-line therapy for chronic lymphocytic leukemia (CLL) is fludarabine plus cyclophosphamide. Adding mitoxantrone (FCM) or rituximab (FCR) appears to improve responses although no large randomized trials have been reported. We report a randomized Phase II trial of FCM and FCM-R in relapsed CLL. FCM was oral fludarabine (24mg/m² for 5 days) and cyclophosphamide (150mg/m² for 5 days) plus i.v. mitoxantrone (6mg/m²) on Day 1 of each cycle. FCM-R was identical with rituximab on Day 1 of each cycle (375mg/m² cycle 1; 500mg/m² cycles 2 to 6). Prophylaxis with aciclovir and co-trimoxazole was given. The primary end-point was response by NCI Criteria 2 months after therapy. Complete remission with incomplete marrow recovery (CR(i)) was defined according to the 2007 CLL Guidelines - clinical CR with a morphologically normal marrow but persistent cytopenias (i.e. platelets <100x10⁹/l and/or neutrophils <1.5x10⁹/l). In addition, minimal residual disease in the marrow was studied 2 months after therapy by four-color flow cytometry with MRD negativity defined as <0.01% CLL cells. 52 patients were entered into the trial with 26 in each arm. The median age was 65 (32–79) with 79% men. 42% had a β2m >4. The median number of prior therapies was 2 (1–6), 31 had prior fludarabine and 6 (12%) were refractory to or relapsed <6 months after fludarabine. 26/44 (59%) had unmutated V_H genes (15/22 FCM-R; 11/22 FCM). 11 patients had deletion of 11q (FCM-R 5, FCM 6) and 1 patient had >20% 17p deleted cells (FCM-R). 36/52 (69%) received 4 or more cycles of therapy with no difference between FCM and FCM-R (18/26). Responses are shown in the Table. 35 SAE’s were reported in 23 patients. There was no difference in the number of patients with SAE’s between the arms (FCM 11, FCM-R 12). 6/7 patients (86%) who had 4 or more prior therapies reported an SAE, compared to 17/45 patients (38%) who had less than 4. 16 SAE’s were suspected to be related to FCM-R and 10 related to FCM. In summary, FCM-R is an effective therapy for relapsed CLL with over two-thirds of patients responding. The study design does not allow a statistical comparison between FCM and FCM-R but the results suggest that adding rituximab to FCM results in a higher complete response rate (CR + CR i = 43% for FCM-R and 13% for FCM) with more patients achieving MRD negativity (5 after FCM-R; 2 after FCM). The results of this randomised Phase II trial justify the study of FC with mitoxantrone and/or rituximab in larger randomized Phase III trials.