MO3-8-2Characteristics and prognosis of leptomeningeal metastasis in patients with breast cancer

Abstract Background The incidence of leptomeningeal metastasis (LM) in breast cancer is reported to be approximately 5% and prognosis of breast cancer patients with LM is poor. Characteristics and treatment for breast cancer with LM remain unclear. The objective of this study is to observe outcome of breast cancer patients with LM in the current background. Patients and methods: We retrospectively reviewed 84 breast cancer patients who were diagnosed with LM and received treatment for LM between 2005 and 2018 in our institution. LM was diagnosed by brain imaging and/or lumbar puncture with the presence of malignant cells in cerebrospinal fluid. Results: Median age at diagnosis of LM was 56.5 years (33-76). Thirty-nine (46%), 7 (8%), 12 (14%), and 24 (29%) were HR+/HER2-, HR+/HER2+, HR-/HER2+ and triple negative, respectively. Median time to LM from the diagnosis of distant metastasis was 66.6 months, and significantly longer in HR+/HER2+ compared with other subtypes (p