Concomitant administration of chlorambucil limits dose intensity of fludarabine in previously treated patients with chronic lymphocytic leukemia.

Fifteen patients with chronic lymphocytic leukemia (CLL) were treated in a phase I-II study of chlorambucil with an escalating dose of fludarabine. The study was designed to identify a maximum tolerated dose (MTD) of fludarabine given in conjunction with a constant dose of chlorambucil. Patients were eligible for study if they had Rai intermediate or high-risk disease which had relapsed from or was refractory to conventional treatment. The initial cohort of patients received fludarabine 10 mg/m2/d days 1-5 and chlorambucil 20 mg/m2 days 1 and 15. Cycles were repeated every 28 days. Unacceptable toxicity was encountered in this cohort. The protocol was then modified to give chlorambucil 20 mg/m2 on day 1 (only). At this chlorambucil dose, cohorts of three patients were treated with fludarabine 10, 15, and 20 mg/m2/d x 5 days. The predominant toxicity was thrombocytopenia with 73% experiencing grade > or = 3 toxicity. The dose-limiting non-hematologic toxicity was infection. We identified an MTD of fludarabine of 15 mg/m2/d x 5 days when given with chlorambucil 20 mg/m2 for this group of patients. One patient achieved a CR and three patients achieved a PR for a total response rate of 27%. We conclude that concomitant administration of chlorambucil limits the dose intensity of fludarabine which can be administered to previously treated patients with CLL.