[A case of recurrent breast cancer with liver metastases showing good response to combination therapy with S-1 plus trastuzumab].

: Here, we report the case of a patient with recurrent breast cancer and multiple liver metastases who showed complete remission (CR) after S-1 plus trastuzumab therapy. A 54-year-old woman with stage IIIA left breast cancer received 4 courses of epirubicin hydrochloride plus cyclophosphamide hydrate therapy and 4 courses of paclitaxel therapy as initial treatment after mastectomy. At 10 months after surgery, the carcinoembryonic antigen (CEA) level increased to 79.0 ng/mL, and multiple liver metastases were detected on close examination. Subsequently, the patient received S-1 plus trastuzumab combination therapy. The CEA level returned to normal after 2 courses of the combination therapy, and the liver metastases disappeared after 5 courses of therapy. CR has been maintained for 1 year and 3 months after the initiation of treatment. Because the present treatment has superior tolerability and safety, it is considered an effective option for treating recurrent breast cancer.