Progressive central nervous system metastases in responder patients for outside central nervous system metastases on trastuzumab-based therapy--report of two cases of refractory breast cancer.

We report two cases of central nervous system (CNS) metastases during systemic response to trastuzumab in combination with chemotherapy for refractory breast cancer. The patients responded to trastuzumab in combination with chemotherapy. During combination treatment, the patients developed cerebellar metastases. A follow-up computed tomography scan revealed that their diseases continued to respond outside the CNS. These cases suggest that the failure of trastuzumab to cross the blood-brain barrier may compromise its overall effectiveness and raises the possibility that CNS metastasis may become clinically more significant in patients receiving antibody-based therapies, including patients responding to therapy outside the CNS. Additionally, repeated stereotactic radiosurgery as gammaknife combination therapy synchronously with systematic trastuzumab-based therapy was useful for the treatment of metastatic breast carcinoma.