Phase II clinical trial of metronomic chemotherapy with combined irinotecan and tegafur-gimeracil-oteracil potassium in metastatic and recurrent breast cancer.

BACKGROUND: We investigated the efficacy and safety of metronomic chemotherapy with combined irinotecan and tegafur-gimeracil-oteracil potassium (TS-1) in patients with metastatic and recurrent breast cancer (MRBC), and the association between irinotecan metabolizing enzyme UDP-glucuronosyltransferase 1A1 (UGT1A1) gene polymorphisms and adverse events.

METHODS: The study group comprised 40 patients aged 35-79 years. Irinotecan (60 mg/m(2) in 5 % dextrose) was administered by 120-min infusion on days 1, 8, and 15 every 4 weeks. TS-1 (prescribed in a standard quantity) was administered at 80 mg/m(2)/day orally on days 3-7, 10-14, and 17-21 every 4 weeks.

RESULTS: Tumor response data were available for 34 patients. Median follow-up was 12 months (range 1-45 months). Response rate was 47 % (one complete and 15 partial responses). Stable disease was observed in 17 patients (50 %). One patient had disease progression (3 %). Median progression-free survival was 14 months [95 % confidence interval (CI), 10-26]. Median overall survival was 26 months (95 % CI not calculable owing to sample size), and 79.3 % of patients survived for 1 year. The most common grade 3 or 4 adverse events were neutropenia (15 %), leukopenia (12.5 %), diarrhea (7.5 %), and anemia (2.5 %). All other adverse events were grade 1 or 2. Treatment-related toxicity was generally modest and manageable. No significant correlation was observed between UGT1A1 polymorphisms and hematological or non-hematological toxicities.

CONCLUSIONS: Metronomic chemotherapy with combined irinotecan and TS-1 was effective in MRBC patients. Adverse effects were mild and the regimen was safely administered without identifying UGT1A1 polymorphisms.