Multi-Institutional Outcomes Following Stereotactic Radiosurgery for Gastrointestinal Brain Metastases

Abstract

Outcomes following stereotactic radiosurgery (SRS) for gastrointestinal (GI) brain metastases (BM) are poorly defined. We analyzed our multi-institutional database of SRS patients, comparing outcomes between GI and non-GI BM patients after SRS. We retrospectively identified all patients completing an initial SRS course across two institutions from 1/2015-12/2020. Demographic and clinical parameters were manually captured. Intracranial progression (ICP) was defined as any concern on post-SRS imaging for recurrence determined by multidisciplinary consensus. Overall survival (OS) and freedom from ICP (FFICP) were estimated via Kaplan Meier models. Cox proportional hazard models were used to assess associations between ICP and parameters. Among 1383 total patients completing SRS for BM, 102 (7.4%) had GI BM. Among these, 46 (45.1%) were of colorectal (CRC) and 34 (33.3%) esophageal origin. Other GI sites (21.6%) included anal, pancreatic, gastric, GI of unknown origin, and hepatocellular carcinoma. Median follow up was 8.7 mos. GI BM patients were more likely to be younger (mean 59.1 vs 63.5 yrs, p = 0.001), male (56.9% vs 44.3%, p = 0.014 ), have more extracranial metastases (mean 1.9 vs 1.6, p = 0.003), have received systemic therapy (73.5% vs 63.9%, p = 0.049) or resection of BM (45.1% vs 25.0%, p < 0.001) prior to SRS, have larger planned target volumes of all BMs (mean 20.3 ccs vs 15.0 ccs, p = 0.013), and were less likely to receive whole brain radiation therapy (WBRT) prior to SRS (3.9% vs 10.8%, p = 0.028) or systemic therapy after SRS (54.9% vs 68.9%, p = 0.004). Among GI patients, median OS was 28.2 mos (95% CI 16.5-35.3), with no significant differences between GI and non-GI patients (p = 0.220) or among GI subgroups (CRC vs other GI: p = 0.731; esophageal vs other GI: p = 0.478). Median FFICP was significantly worse for GI patients (6.2 mos, 95% CI 4.0-9.6 mos) than for non-GI patients (12.4 mos, 95% CI 10.8-13.9 mos; p = 0.004). After accounting for age, sex, performance status, number of irradiated BMs, extracranial disease burden, extracranial disease control, interval from primary cancer diagnosis to BM diagnosis, resection status, receipt of prior WBRT, and receipt of post-SRS systemic therapy, GI origin was significantly associated with worse FFICP (HR 1.50, 95% CI 1.15-2.02, p = 0.007). FFICP was not significantly different between GI subgroups, with CRC and esophageal patients demonstrating median times to ICP of 5.0 mos (95% CI 3.4-9.6) and 7.2 mos (95% CI 2.7-14.1), respectively. Only 2 GI patients (2.0%) had ICP at site of prior SRS. Across a modern, multi-institutional SRS cohort comparing GI to non-GI primary patients, BMs of GI origin demonstrated inferior FFICP to those of non-GI origin. OS did not vary significantly across GI and non-GI cases. Among GI subtypes, no significant differences were identified across FFICP or OS. These data may help inform treatment decisions and post-SRS surveillance.