Intrathecal Trastuzumab Treatment in Patients with Breast Cancer and Leptomeningeal Carcinomatosis

Leptomeningeal carcinomatosis is a fatal manifestation of metastatic breast cancer. Investigation of intrathecal (IT) trastuzumab for leptomeningeal carcinomatosis is currently underway; however, there has been no consensus. We report on two cases of human epidermal growth factor receptor 2 positive (HER2+) breast cancer following IT trastuzumab for leptomeningeal carcinomatosis. The first patient was treated with weekly IT 15 mg methotrexate plus IT 50 mg trastuzumab for 7 months, followed by IT trastuzumab (50 mg > 25 mg) for 18 months. The other patient received IT trastuzumab with systemic chemotherapy (trastuzumab and/or paclitaxel) for 13 months. Good control of leptomeningeal disease was achieved with IT trastuzumab in both patients, with survival durations of 20 and 29 months, respectively. We suggest that IT trastuzumab is a promising treatment for patients with HER2+ breast cancer and leptomeningeal carcinomatosis.