Bendamustine in the Treatment of Chronic Lymphocytic Leukemia -Consistent Superiority Over Chlorambucil in Elderly Patients and Across Clinically Defined Risk Groups.

Bendamustine is a purine analog/alkylator hybrid agent with a unique mechanism of action, which has shown good clinical efficacy and acceptable tolerability in various hematological malignancies. Chronic lymphocytic leukemia (CLL) is a disease of the elderly, and presents with a variety of clinical characteristics which influence the prognosis. We analyzed tolerability and efficacy of bendamustine (BEN) in comparison to chlorambucil (CLB) in clinical risk groups defined by age and specific indicators of disease activity.

The efficacy and safety of BEN and CLB have been compared in a randomized, open-label, multicenter, phase III trial in patients with previously untreated advanced (Binet stage B/C) CLL. Patients were randomized to receive BEN (100 mg/m² on days 1 + 2) or CLB (0.8 mg/kg on days 1 and 15) for up to 6 treatment cycles. The primary endpoints were overall remission rate (ORR), which was defined as complete or partial response, and progression-free survival (PFS). Secondary endpoints included overall survival (OS) and safety. The response to treatment was evaluated by a blinded Independent Response Assessment Committee.

A total of 319 patients were randomized (162 bendamustine, 157 chlorambucil), of whom all were included in the efficacy analysis, while 312 were evaluable for safety. Median age was 64 years (35 to 78). The median number of treatment cycles was 6 in both study arms, regardless of an age above or below 65 years. The median observation time was 35 months. ORR was significantly higher with BEN than with CLB (68% versus 31%, P<0.0001). The median PFS was 21.6 months with BEN and 8.3 months with CLB (P<0.0001). So far, there is no difference in OS (median not reached with BEN versus 65.4 months with CLB; p = 0.16). No significant difference in the remission rates became apparent when comparing patients below and above the age of 65 years (ORR 71.6 % versus 63.5 % with BEN, p>0.3; and 28.4 % versus 32.5 % with CLB, p>0.6). PFS was not influenced by age above 65 years, stage of disease (Binet stage B versus C), or elevated LDH. However, patients without B symptoms had a longer median PFS with BEN than those patients with B symptoms (30.4 months versus 17.7 months; p<0.0001), whereas median PFS was not affected by the presence of B symptoms in patients with CLB (8.9 months in both patient groups).

This study has shown that bendamustine offers significantly greater efficacy than chlorambucil in the elderly and across clinically defined major risk groups, even in the presence of B symptoms. BEN should be considered as first-line chemotherapy for patients with advanced CLL.

Knauf:mundipharma: Consultancy, Honoraria; cephalon: Consultancy, Honoraria. Klein:mundipharma: Consultancy, Honoraria. Merkle:mundipharma: Consultancy, Honoraria. Montillo:mundipharma Italy: Consultancy, Research Funding.