372PVentriculoperitoneal shunt for CNS metastasis in breast cancer: Clinical outcomes based on intrinsic subtype

Abstract Background Leptomeningeal metastasis (LM) is associated with grave prognosis in breast cancer (BC) and can be treated with ventriculoperitoneal shunt (VPS). Information regarding LM and VPS based on intrinsic subtype is limited; thus, in the present study, the clinical outcomes of BC treated with VPS were investigated. Methods The present retrospective study included 70 patients diagnosed with LM and who received VPS. The patients were divided into four groups based on BC subtype: hormone receptor (HR)+HER2-, HR+/HER2+, HR-/HER2+, and triple negative BC (TNBC). Results The median age at the time of diagnosis with LM was 49 years (range 30–69 years). Isolated central nervous system (CNS) metastasis was observed in 37.1% (26/70) of patients, and more than half of the patients (47/70, 67.1%) received whole brain radiotherapy (WBRT) before and/or after VPS. The median overall survival (OS) after CNS metastasis was significantly longer in HR-/HER2+ patients (16.2 months, 95% confidence interval, CI 13.7–18.6, p = 0.009), and anti-HER2 treatment was identified as a significant prognostic factor for better OS based on multivariate analysis (hazard ratio, HR 0.15, 95% CI 0.04–0.57, p = 0.005). TNBC was correlated with shorter OS after CNS metastasis (HR 2.82, 95% CI 1.46–5.48, p = 0.002). The median OS after VPS was 2.3 months (95% CI 1.8–2.7) in all patients, and 6-months OS rates after VPS were 0% and 3.9% in HR-HER2+ and in TNBC, respectively. Conclusions The clinical outcome of BC patients after CNS metastasis who received VPS was significantly different in real-world clinical setting based on intrinsic subtype. Anti-HER2 treatment should be attempted after CNS metastasis in HER2+ patients. However, the survival of metastatic BC (MBC) after VPS remains poor, especially in HR-/HER2+ and TNBC subgroups. Further investigations are required to improve the prognosis of LM. Legal entity responsible for the study Yeon Hee Park. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.