Determinants of symptomatic intracranial progression following an initial stereotactic radiosurgery course

Purpose : Clinical and imaging surveillance of patients with brain metastases (BMs) is important after stereotactic radiosurgery (SRS), as many will experience intracranial progression (ITCP) requiring multidisciplinary management. The prognostic significance of neurologic symptoms at the time of ITCP is poorly understood. Materials/Methods This was a multi-institutional, retrospective cohort study from 2015-2020, including all patients with BMs completing an initial course of SRS. The primary outcome was overall survival (OS) by presence of neurologic symptoms at ITCP. OS, freedom from ITCP (FF-ITCP), and freedom from symptomatic ITCP (FF-SITCP) were assessed via Kaplan-Meier method. Cox proportional hazard models tested parameters impacting FF-ITCP and FF-SITCP. Results : Among 1383 patients, median age was 63.4 years, 55% were female, and common primaries were non-small cell lung (49%), breast (15%), and melanoma (9%). At a median follow up of 8.72 months, asymptomatic and symptomatic ITCP were observed in 504 (36%) and 194 (14%) patients respectively. The majority of ITCP were distant ITCP (79.5%). OS was worse with SITCP (median 10.2 vs 17.9 months, p<0.001). SITCP was associated with clinical factors including total treatment volume (P = 0.012), melanoma histology (P = 0.001), prior WBRT (P = 0.003), number of brain metastases (P < 0.001), interval of 1-2 years from primary and brain metastasis diagnosis (P = 0.012), controlled extracranial disease (P = 0.042), and receipt of pre-SRS chemotherapy (P = 0.015). Patients who were younger and received post-SRS chemotherapy (P = 0.001), immunotherapy (P < 0.001), and targeted or small-molecule inhibitor therapy (P < 0.026) had better FF-SITCP. Conclusions : In this cohort study of BM patients completing SRS, neurologic symptoms at ITCP is prognostic for OS. This data informs post-SRS surveillance in clinical practice as well as future prospective studies needed in the modern management of BMs.