[An early phase II study of CPT-11 (irinotecan hydrochloride) in patients with advanced breast cancer].

An early phase II study of irinotecan (CPT-11) in patients with advanced or recurrent breast cancer was undertaken by a cooperative study group of 15 institutes in Japan. CPT-11 was administered by intravenous drip-infusion. The administration schedules were 100 mg/m2 weekly (regimen A), 150 mg/m2 biweekly (regimen B), and 200 mg/m2 every 3-4 weeks (regimen C). There were 4 partial responses (PRs), 12 cases with no changes (1 minor response) and 9 cases of progressive diseases with a response rate of 16% (4/25). One out of 7 patients on regimen A and 3 patients out of 15 patients on regimen C achieved PR with a response rate of 14% and 20%, respectively. In three out of 4 PRs, prior chemotherapy, endocrinotherapy or radiotherapy had failed. Major adverse reactions were leukopenia 28/33 (85%), neutropenia 19/25 (76%), anemia 15/33 (46%), nausea/vomiting 28/33 (85%), anorexia 25/33 (76%), diarrhea 22/33 (67%) and alopecia 20/33 (61%). The incidence of leukopenia and thrombocytopenia seemed to be higher in regimen C than regimen A, and diarrhea was also more severe in regimen C than regimen A. The recovery of leukopenia was delayed in some patients on regimen C. The results suggested that CPT-11 was effective against advanced or recurrent breast cancer. The recommended administration schedule for a late phase II study was thought to be 100 mg/m2 weekly, considering efficacy and safety.