[A case of paclitaxel and trastuzumab-resistant recurrent breast cancer with liver metastasis responding to S-1].

We experienced a case of paclitaxel- and trastuzumab-resistant recurrent breast cancer with liver metastases showing significant improvement by S-1. A 76-year-old woman was diagnosed with left breast cancer (T2N1M0, Stage II B). She received total mastectomy and CEF (cyclophosphamide 500 mg/m(2), epirubicin 60 mg/m(2), 5-FU 750 mg/m(2)) as adjuvant chemotherapy in March 2004. But twelve months later, she was referred to our clinic for management of lung and left supraclavicular lymph node metastases. Then weekly paclitaxel (80 mg/m(2)) and trastuzumab were started. After 2 cycles of weekly paclitaxel and trastuzumab treatment, lung and lymph node metastases were reduced and the patient showed a clinical response (CR), so she was treated by trastuzumab only. But seven months later, she was diagnosed as a recurrence of liver metastases. She was treated by combined paclitaxel and trastuzumab again, but liver metastases and tumor marker were progressive. S-1 was administered orally 100 mg/day every day for 4 weeks, followed by a 2-week rest interval as 1 cycle, and trastuzumab was injected at 2 mg/kg/week for every weeks. After 2 courses of the treatment, the level of tumor marker and tumor size of liver metastases were reduced. Only rash (grade 1) was observed during treatment. The treatment of S-1 is thought to be effective for taxane-resistant recurrent breast cancer.