Phase II study of bi-weekly irinotecan for patients with previously treated HER2-negative metastatic breast cancer: KMBOG0610B

Background: A trial was conducted to evaluate the feasibility, efficacy, and safety of biweekly administration of irinotecan, a novel topoisomerase I inhibitor, for patients with metastatic breast cancer (MBC) previously treated with either anthracycline-based or taxane-based chemotherapy. Methods: Eligible patients were HER2-negative, had a performance status of 0 to 2, and had been treated previously with either anthracyclines or taxanes for MBC. Patients received irinotecan intravenously at 150 mg/m² on days 1 and 15 every 4 weeks. The primary end-point was feasibility, and the treatment was considered feasible if a patient was able to receive three administrations of irinotecan within the first 8 weeks, as pre-specified in the protocol. Results: Eighteen patients (median age 60 years) were enrolled. Fifteen patients received irinotecan more than 3 times within the first 8 weeks, with resulting feasibility of 83.3%. The median number of treatment cycles was 2 (range 1-16) during this period, and the relative dose intensity was 91.2%. Partial response was observed for one patient, so overall response rate was 5.6%. Nine patients (50.0%) had stable disease, and overall disease control was 50.0%. Median progression-free survival and overall survival periods were 3.2 and 9.6 months, respectively. The only grade 3/4 hematological toxicity was neutropenia (22.2%). Grade 3/4 non-hematological toxicities were anorexia (11.2%), diarrhea (11.2%), and fatigue (5.6%). No treatment-related death occurred. Conclusions: This study demonstrated that biweekly administration of 150 mg/m² irinotecan was feasible for patients with MBC treated previously with anthracyclines or taxanes.