[Three cases of metastatic breast cancer effectively treated with S-1 therapy]

We experienced 3 cases of recurrent breast cancer treated with S-1 therapy, delaying tumor progression and improving their quality of life (QOL). All the patients had been previously treated with both anthracyclines and/or taxanes prior to S-1 chemotherapy. All patients almost completed the full dose through the whole course of treatment, and the drug showed good tolerability. Long-term(more than 12 weeks)therapeutic efficacy and the patients' QOL have been maintained for all patients. No major side effects were seen. It is thought that less toxicity enabled patient 3 to undergo long-term therapy. It is especially important that one patient had therapeutic efficacy and QOL improvement from treatment with S-1 and aromatase inhibitor for over 3 years, after being treated with anthracyclines, taxanes and vinorelbine. We conclude that S-1 is effective and well tolerated in patients with metastatic breast cancer, and will accommodate a long-time progression with respect to efficacy and maintaining the patients' QOL. Further evaluation of S-1 is necessary to elucidate its clinical role in breast cancer treatment.