[A late phase II clinical study of S-1 in patients with progressed, refractory breast cancer]

A late phase II clinical study of S-1 against advanced or refractory breast cancer was done by 37 institutes in Japan. S-1 was administered twice daily at 80, 100 or 120 mg/body/day consecutively for 28 days followed by 14 days of rest (1 course). Eighty-three patients were enrolled and 81 were eligible for the study. The response ratio was 42.0% with 6 CR and 28 PR and its 95% confidence interval for the response was 31.1 to 53.5%. The median survival period was 910 days (95% confidence interval was 493-1, 083 days). The observed major adverse reactions (> or = grade 2) were as follows: hematological toxicities: leukopenia 21.0% (17/81), neutropenia 28.4% (23/81), erythropenia 4.9% (4/81); gastrointestinal toxicities: anorexia 9.9% (8/81), nausea and vomiting 12.3% (10/81), diarrhea 8.6% (7/81), stomatitis 1.2% (1/81), and fatigue 8.6% (7/81). The severe adverse reactions (> or = grade 3) were as follows; hematological toxicities: neutropenia 8.6% (7/81), anorexia 4.9% (4/81), fatigue 3.7% (3/81), nausea and vomiting 1.2% (1/81), diarrhea 1.2% (1/81), stomatitis 1.2% (1/81). Grade 4 adverse reactions (neutropenia and fatigue) were observed only in 1 patient. The ratio without hospitalization was 87.7%. These results strongly suggest the superior efficacy and safety of S-1 against patients suffering from advanced, refractory breast cancer. Therefore, S-1 may be a new therapeutic agent to prolong the survival period of breast cancer patients due to its high antitumor activity and low toxicity.