Purpose: To define the maximum tolerated dose (MTD) of irinotecan (CPT-11) given on days 1 and 8 with mitomycin C (MMC) given on day 1 in a monthly cycle, and to assess the toxicity and activity of this regimen in patients with previously treated colorectal carcinoma.
Methods: Fifty-two patients, all pretreated with adjuvant 5-fluorouracil (20 patients) and/or one (35 patients) or two (8 patients) lines of chemotherapy, were entered in this study. Escalating doses of CPT-11 (starting from 150 mg/m2) were administered on days 1 and 8, with escalating doses of MMC (starting from 8 mg/m2) given on day 1, recycling every 28 days. At least 3 patients were treated at each dose level. Escalation proceeded unless 2 out of 3 or 4 out of 6 patients experienced a dose-limiting toxicity (DLT) after the first cycle.
Results: Twelve patients were entered in the phase I study, and 4 consecutive dose levels were tested. At the last dose level (CPT-11 200 mg/m2 plus MMC 10 mg/m2) 4 of 6 patients experienced a DLT (i.e., grade 4 neutropenia in 2 patients and grade 3 diarrhea in 2 patients). Therefore, this dose level was considered as the MTD. Forty patients were treated at the previous dose level (CPT-11, 175 mg/m2 plus MMC 10 mg/m2). One complete, 4 partial, 3 minor responses and 11 cases of stable disease were registered, giving a response rate of 12% [95% confidence interval (CI), 4-27%] and an overall control of tumor growth in 47% (95% CI, 31-64%) of patients. The median time to treatment failure was 6 months (range 1-19+). The median survival time was 14.5 months, and the 1-year and 2-year probability of survival were 56 and 43%. Neutropenia and diarrhea affected 62 and 58% of patients, grade 3 or 4 being registered in 26 and 23% of them, respectively. One episode of neutropenic fever was reported. Other acute toxicities were usually mild and manageable.
Conclusions: CPT-11 175 mg/m2 on days 1 and 8 associated with MMC 10 mg/m2 on day 1, every 4 weeks, is a safe and moderately active regimen in heavily pretreated patients with advanced colorectal carcinoma. The role of MMC in this combination is doubtful, and further attempts with other new agents should be made to improve the outcome in these patients.