Phase I clinical and pharmacokinetic study of irinotecan, fluorouracil, anti leucovorin in patients with advanced solid tumors

Purpose: To determine the maximum-tolerable dose (MTD) of fluorouracil (5FU) when given with fixed doses of leucovorin and irinotecan (CPT-11), to define the dose-limiting toxicities of this combination, and to evaluate the effect of 5FU on the pharmacokinetics of CPT-11. Patients and Methods: CPT-11, leucovorin, and 5FU were administered in repeated 6-week cycles that consisted of weekly treatment with all three drugs for 4 consecutive weeks followed by a 5-week break. On day 1 of treatment, CPT-11 alone was given by 90-minute infusion, and pharmacokinetic sampling was performed over 24 hours. Leucovorin and 5FU were administered by brief intravenous injection on day 2. On days 8, 15, and 22, CPT-11 infusion was immediately followed by leucovorin and then 5FU. A second 24-hour pharmacokinetic sampling was performed on day 8, which permitted comparison of the pharmocokinetics of CPT-11 with and without 5FU. For the second 6-week cycle, leucovorin was administered first, followed by 5FU and then CPT-11, and a third pharmacokinetic sampling was performed. Results: Forty-two patients were entered onto this trial. The CPT-11 dose was initially fixed at 100 mg/m(2). Leucovorin was fixed at 20 mg/m(2). 5FU doses of 210, 265, 340, 425, and 500 mg/m(2) were studied. When the 500-mg/m(2) dose of 5FU was found to be tolerable, this was then maintained and CPT-11 wets escalated to 125 and then 150 mg/m(2). This final CPT-11 dose exceeded the MTD. Neutropenia was the major dose-limiting toxicity. Diarrhea was common, but wets rarely dose-limiting. Coadministration of 5FU had no substantial effect on the pharmacokinetics of CPT-11 or SN-38. Among the 38 patients with colorectal cancer, six partial responses (PRs) were seen in this predominantly SFU-refractory patient population. Conclusion: 5FU does not substantially affect the metabolism of CPT-11 to its active metabolite, SN-38. The combination of CPT-11 125 mg/m(2), 5FU 500 mg/m(2), and leucovorin 20 mg/m(2) is feasible and tolerable on this schedule. (C) 1996 by American Society of Clinical Oncology.