PHASE-I TRIAL OF LOW-DOSE CONTINUOUS TOPOTECAN INFUSION IN PATIENTS WITH CANCER - AN ACTIVE AND WELL-TOLERATED REGIMEN

Purpose: The objective of this trial was to define the maximum-tolerated dose (MTD) of topotecan for a 21-day infusion schedule, repeated every 28 days, in patients with cancer. Patients and Methods: Cohorts of four patients received continuous ambulatory infusions of topotecan in escalated duration with doses beginning at 0.20 mg/m2/d for 7 days. Forty-four patients with a histologic diagnosis of cancer refractory to standard therapy were treated with infusions of topotecan for a total of 115 cycles and 1,780 patient-days of infusion. The median number of treatment cycles per patient was two (range, one to eight). All patients were heavily pretreated with chemotherapy and/or radiation. Results: The dose-limiting toxicity (DLT) was myelosuppression, with thrombocytopenia greater than neutropenia seen at the dose level of 0.70 mg/m2/d for 21 days. At the MTD of 0.53 mg/m2, ten patients were treated for a total of 20 courses, resulting in one episode of grade 4 thrombocytopenia and leukopenia, one grade 3 thrombocytopenia, and two grade 3 leukopenias. This dose regimen was well tolerated, with minimal nonhematologic toxicity. Local infusion port complications developed in two patients and two had bacteremia, including one patient with repeated local skin infections. Objective responses were observed in this heavily pretreated population for patients with ovarian cancer (two partial responses and one mixed response in six patients), breast cancer (one partial response and one mixed response in two patients), and for one patient each with renal and non- small-cell lung cancer (two partial remissions). Conclusion: Twenty-one-day topotecan infusion is well tolerated at 0.53 mg/m2, with dose-intensity exceeding other schedules for administration of topotecan. The DLT is hematologic, with thrombocytopenia somewhat exceeding leukopenia. Objective responses were observed in seven patients with breast, ovarian, renal, and non-small-cell lung cancer.