Bendamustine Combined with Rituximab (BR) in First-Line Therapy of Advanced CLL: A Multicenter Phase II Trial of the German CLL Study Group (GCLLSG).

Bendamustine has shown considerable activity in monotherapy for lymphoid malignancies including chronic lymphocytic leukemia (CLL). In vitro studies have demonstrated synergistic pro-apoptotic effects of bendamustine and the CD20 antibody rituximab (BR) in primary CLL cells. Encouraging results have also been obtained using the BR combination treatment in previously treated CLL. This multicenter phase II trial (CLL2M) is the first study assessing the efficacy and toxicity of bendamustine in combination with rituximab in previously untreated CLL patients (pts).

Between March 2007 and September 2008 117 pts with untreated CLL requiring therapy were enrolled into the protocol. Bendamustine was given at a dose of 90 mg/m² on day 1 and 2, combined with 375 mg/m² rituximab for the first cycle and 500 mg/m² for subsequent cycles. BR treatment was administered every 28 days for up to 6 courses. Blood samples were taken for analysis by fluorescence in situ hybridization (FISH), the IgV_H mutational status and expression of ZAP70/CD38. Minimal residual disease (MRD) was evaluated in peripheral blood and bone marrow by 4-color flow cytometry.

Data on the entire study population of 117 pts (median age 64 years) with a total of 583 treatment cycles are available. As of June 2009 the median observation time was 15.4 months (mo). 11.1% of the pts presented with stage Binet A, 41.0% with Binet B and 47.9% with Binet C disease. A mean number of 5.0 courses were delivered. 114 pts were evaluable for toxicity, 110 for response and 113 for progression free survival (PFS). The most frequent adverse events based on 583 treatment cycles were myelosuppression and infections: grade 3/4 anemia occurred in 4.9%, grade 3/4 leukopenia in 14.6%, grade 3/4 neutropenia and thrombocytopenia in 6.5% and 6.1% of all given courses, respectively. 29 episodes of CTC grade >3 infections were documented (5.1% of all courses). Treatment related mortality occurred in 2.6% of the pts: one liver failure after attempt of suicide with antihistamines, one fatal pneumonia and one sepsis in neutropenia. The overall response rate was 90.9% with 32.7% (36 pts) clinical complete remissions (CR). A nodular partial remission (nPR) was achieved in 2.7% (3 pts) and a partial response (PR) in 55.5% of the pts (61 pts), respectively. 9.1% of the pts (10 pts) had stable disease (SD) whereas none of the pts was progressive (PD). After 18 mo 75.8% of the pts were still in remission, median PFS has not been reached. An MRD level below 10E-4 was observed after completion of therapy in 29 of 50 evaluable pts in peripheral blood, while 7 of 25 pts achieved MRD negativity in bone marrow. Differences in response were observed among the genetic subgroups: 19 of 21 pts with 11q- achieved a remission with 10 PR and 9 CR (ORR: 90.5%). Accordingly, 17 of 19 patients with +12 responded (14 PR, 3 CR, ORR: 89.5%). In the high-risk group with 17p-, 3 of 7 pts showed a partial response (ORR: 42.9%). 56 of 63 pts (ORR: 88.9%) with unmutated IgV_H status responded to BR.

Bendamustine plus rituximab (BR) is effective and safe in the first-line treatment of CLL. Major side effects (myelosuppression and infections) were infrequent. Based on these encouraging phase II data the German CLL Study group is presently investigating the efficacy of BR in comparison to fludarabine-based immunochemotherapy (FCR) in the first-line treatment of CLL within a randomized phase III trial (CLL10 protocol).

Fischer:Roche: travel expenses. Cramer:Roche: travel grants. Stilgenbauer:Bayer: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding. Fink:Roche: . Boettcher:Roche: Research Funding. Ritgen:Roche: Research Funding. Kneba:Roche: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Döhner:Roche: Research Funding. Eichhorst:Roche: Honoraria, Research Funding; Mundipharma: Research Funding; Hospira: Honoraria. Hallek:Roche: Consultancy, Honoraria, Research Funding. Wendtner:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer Schering: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.