[A case of capecitabine-resistant recurrent breast cancer found to be responsive to S-1]

Thirteen months following surgery, local recurrence and multiple lung metastases occurred. Hormone therapy was continued following the recurrence but was found to be ineffective, so the patient was referred to our hospital 9 months after the recurrence. Capecitabine-based chemotherapy was administered but found to be ineffective; 3 months later, the anti-cancer drug was changed to S-1. After 3 months of S-1 administration, a CT scan showed a marked reduction in sites of recurrence and metastasis, making it possible to control progression of the disease over a longer period. No critical adverse reactions were observed, suggesting that S-1 can be useful and safe for the treatment of capecitabine-resistant recurrent breast cancer.