CMET-41. OUTCOMES FOLLOWING STEREOTACTIC RADIOSURGERY (SRS) FOR LIMITED BRAIN METASTASES - AN AUSTRALIAN SINGLE INSTITUTIONAL EXPERIENCE

Abstract

Abstract INTRODUCTION Despite increasing use of stereotactic radiosurgery (SRS) for management of brain metastases (BM), published Australian data is scarce. We aim to report on the outcomes following SRS for limited BM in a single Australian institution. METHODS This is a retrospective cohort of patients with limited BM treated with SRS between August 2015 and March 2019. A dose of 24Gy/3# were prescribed to intact lesion, and 21Gy/3# to surgical cavity post-surgical resection. All patients were followed with 3-monthly surveillance MRI brain. Primary outcomes were: local failure (LF: increased in size of SRS-treated BM lesion/ recurrence in surgical cavity), distant failure (DF: intracranial progression outside of the SRS-treated lesion/ cavity), and overall survival (OS). LF, DF and OS were estimated using the Kaplan-Meier method. Multivariate Cox regressions were used to evaluate factors associated with outcomes of interest, with death as competing-risk events for LF and DF. RESULTS 76 courses of SRS were delivered in 65 patients (54 unresected BM lesions, and 22 surgical cavities). 43 (66%) patients were ECOG 0–1. 35 (54%) patients had solitary BM. 41 (63%) had symptomatic BM. Half of the patients had primary lung cancer. Median follow-up was 4.8 months (range:0.1–39 months). 10 LF were observed at a median of 3.5 month post-SRS, with 6- and 12-month LF cumulative incidence of 14% and 24% respectively. 30 DF were observed at a median of 3.3 months, with 6- and 12-month DF cumulative incidence of 38% and 63% respectively. The 12- and 24-month OS were 39% and 26% respectively. In multivariate analyses, better ECOG status, solitary BM lesion, resection of BM pre-SRS, and use of subsequent systemic therapy were independently associated with improved OS. CONCLUSION This is one of the few Australian series reporting on outcomes following SRS for limited BM, with comparable outcomes to published international series.