[Successful treatment of trastuzumab-resistant HER2-positive breast cancer with extensive liver metastases using the combination of trastuzumab and capecitabine - a case report].

We report a case of a trastuzumab-resistant human epidermal growth factor receptor-2(HER2)-positive breast cancer patient with extensive liver metastases and associated impaired liver function, who showed an excellent response to the combination of trastuzumab and capecitabine. The patient was a 59-year-old postmenopausal woman with multiple liver metastases at first examination. She first received anthracycline-based chemotherapy, and after progression was followed up with a combination of trastuzumab and paclitaxel. Despite an initial response to this treatment, liver metastases rapidly progressed. Although palliative treatment was considered because of her impaired liver function, she received capecitabine while continuing trastuzumab. This combination therapy showed an excellent response, and a good quality of life(QOL)was maintained for a long time without any severe adverse events. The continuation of trastuzumab is considered effective after having progressed by trastuzumab including pretreatment, and we consider it worth while to give a combination of trastuzumab and capecitabine to patients with extensive liver metastases and associated impaired liver function, because of the treatment's synergistic effect and low risk of causing severe adverse events.