EPID-02. STEREOTACTIC RADIOSURGERY AND CHEMOTHERAPY TREATMENT PATTERNS IN BREAST CANCER BRAIN METASTASES

Abstract

Abstract Brain metastases (BM) are typically treated with systemic chemotherapy and stereotactic radiosurgery (SRS). Population-level studies exploring SRS use in different patient populations and its impact on chemotherapy treatment patterns are needed. This study examines data from Surveillance, Epidemiology, and End-Results (SEER) from 2010–2012 and Medicare claims from 2008–2014 to identify the utility of SRS and associated chemotherapy treatment patterns in the breast cancer BM patient population. 25,954 breast cancer patients were identified, of which 6,657 (26%) received SRS. Chi-square and Fisher’s exact tests were used for initial univariate analyses. Univariable logistic regression models were fit for each predictor and multivariable models were selected using LASSO. Compared to patients without SRS, patients who received SRS were older, diagnosed at later disease stages, and less likely to have the Her2-/HR+ subtype. Patients with SRS most commonly received aromatase inhibitors (53.5%), followed by selective estrogen receptor modulators (SERM; 31.7%), taxanes (27.2%), alkylating agents (21.2%), monoclonal antibodies (22.2%), antimetabolite drugs (18.3%), anthracyclines (11.4%), and platinating agents (6.8%). Increased odds of SRS were associated with drug classes including taxanes (aOR: 1.29), monoclonal antibodies (aOR: 1.67), antimetabolites (aOR: 1.77), anthracyclines (aOR: 1.32), and topoisomerase-II inhibitors (aOR: 3.16). Aromatase inhibitors were associated with decreased odds of SRS use (aOR: 0.84). Alkylating agents, platinating agents, and SERM had no such associations. Our findings suggest that use of many chemotherapeutic agents increases with SRS regardless of ability to penetrate the blood-brain-barrier and parallels standard systemic breast cancer treatments. Because large-scale studies on the impact of SRS on breast cancer BM patients are lacking, it is important to identify differences in treatment usage and patterns. Important clinical implications regarding drug usage frequency, adherence to treatment guidelines, and use of different agents across SRS patients may arise by analyzing differences amongst and between populations of patients with and without SRS.