[A Case of Stage IV Breast Cancer with Extensive Metastasis Successfully Treated with S-1 plus Anastrozole Therapy].

We report the case of a patient in which S-1 plus anastrozole was administered as first-line chemotherapy for Stage IV breast cancer with skin invasion, multiple lymph node metastasis, and lymphangitis carcinomatosis. A 77-year-old woman had a mass destroyed immediately outside the axilla with dry coughs. An 11mm unpalpable mass in the right breast and an axillary mass were confirmed to be scirrhous carcinoma(Luminal type B), respectively, by core needle biopsy. In one course, S- 1(100mg/day)therapy involves taking 2 courses of 14 days of administration and 7 days off the drug. Anastrozole(1mg/ day)was administered daily. After completion of one course, marked shrinkage of the axillary tumor and supraclavicular lymph node, and lightness of coughing was observed. The metastatic lymph nodes and pulmonary metastatic lesions reduced in size by over 30%, as revealed using CT. The adverse event was only grade 1 pigmentation and lacrimation. Ten months later, the self-destructed skin was completely scarred, and metastatic lesions had maintained their reduction in size. According to the results of the SELECT BC study, S-1 as primary chemotherapy for breast cancer is an evidence-based drug that can reduce the decrease in QOL, such as hair loss, and it can be positively selected.