Treatment of refractory chronic lymphocytic leukemia with prednimustine: a phase II study using strict response criteria.

Twenty-one patients with refractory chronic lymphocytic leukemia (CLL) were entered into this Northern California Oncology Group (NCOG) study of prednimustine, an ester of chlorambucil and prednisolone. All patients had active disease and were refractory to standard alkylating agent chemotherapy. Treatment consisted of prednimustine 100 mg/m2/day orally for 3 consecutive days every 2 weeks. By strict response criteria used in this study there was one complete remission (CR), no partial remissions (PR), and three cases of clinical improvement (CI) in 18 evaluable patients, for a total response rate of 22%. The median duration of response is 20+ months, with two patients continuing to respond. Toxicity of this intermittent prednimustine regimen consisted primarily of mild to moderate thrombocytopenia and neutropenia. No episodes of treatment-associated infection or hemorrhage occurred, and nonhematologic toxicity was minor. Using strict response criteria, this study fails to confirm previous reports of high response rates for prednimustine in patients with CLL refractory to standard therapy. The significance of the response category of clinical improvement in CLL is demonstrated by the substantial improvement in objective parameters and the long duration of response. This study also emphasizes the need for standardization of response criteria for this disease.