TRSC-02 Response to Parp Inhibitors in Patients With Breast Cancer Metastatic to the Central Nervous System

BACKGROUND Central nervous system (CNS) metastasis from breast cancer can be challenging to treat due to the limited blood brain barrier penetration of many systemic therapies. The goal of our study is to describe the clinical benefit of PARP inhibitors (PARPi) in patients with breast cancer CNS metastasis. METHODS This retrospective case series was conducted at three academic cancer centers (Johns Hopkins, Dana-Farber, and Duke) and included patients with the following criteria: age≥18 years with a breast cancer diagnosis (any subtype); diagnosis of parenchymal brain metastasis or leptomeningeal disease (LMD); and received PARPi for CNS metastasis. Descriptive statistics, Kruskal-Wallis rank sum tests, and Kaplan-Meier analyses were performed. RESULTS Although this analysis includes one center’s experience, we will present a combined dataset (N = 45) at the main conference. 11 patients were identified at Johns Hopkins. 4 (36.4%) were Black and 6 (54.5%) were White; 6 (54.5%) had ER+HER2- disease and 5 (45.5%) had TNBC; 5 (45.5%) had BRCA1 mutations and 5 (45.5%) had BRCA2 mutations. Median lines of therapy prior to PARPi was 6 [1 - 11]. On average, patients remained on PARPi for 5 months [0.5 - 66], and overall survival (OS) time from PARPi to death was 16 months [2 - 66]. Duration of PARPi and OS did not differ significantly between ER+HER2- and TNBC (p=0.74 and 0.69) or BRCA 1 and 2 (p=0.78 and 0.72). Black patients had significantly shorter PARPi duration and survival than White patients (PARPi 2 vs. 8 months, p=0.028 and OS 4 vs 18 months, p=0.028). Prior CNS radiation was significantly associated with longer PARPi duration and survival (PARPi 5 vs 1 month, p=0.02 and OS 17 vs. 3 months, p=0.032). CONCLUSIONS PARPi are associated with significant clinical benefit in patients with breast cancer CNS metastasis. Larger data series will help confirm these observations.