[A case of anthracycline- and taxane-resistant recurrent advanced breast cancer successfully treated with S-1 monotherapy].

We experienced a case of anthracycline- and taxane-resistant recurrent breast cancer with multiple liver metastases and multiple bone metastases showing marked improvement by S-1. A 52-year-old woman visited our hospital because of her liver dysfunction in May 2008. She underwent a partial mastectomy preserving chest muscles in another hospital in 2000, but further details were unknown. Radiographic imaging tests revealed multiple metastases to the liver and bones in May 2008, and she was referred to our hospital for management of metastatic lesions. Tumor of the liver was diagnosed as metastases from the breast carcinoma, ER+, PgR+, HER2 (0), and histopathologically by core needle biopsy under ultrasonography. She received 4 courses of EC after 4 courses of biweekly docetaxel treatment. She showed a partial response (PR), so she was treated by the same course of treatment again. But she was diagnosed with an enlargement of liver metastases and recurrence of bone metastases by PET examination. Then the oral treatment with S-1 was started, and at the end of the second course, a significant reduction of abnormal accumulation in PET was noted. She has been quite well without any adverse effects from S-1. S-1 monotherapy was thus considered to be an effective treatment for advanced or recurrent breast cancer resistant to anthracyclines and taxanes.