Mmod-05 the Impact of Egfr Variants on Intracranial Progression Free Survival and Overall Survival in NSCLC Patients With Brain Metastases Undergoing Stereotactic Radiosurgery

Abstract Outcomes for patients with brain metastases (BM) from targetable epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC) have been improved with tyrosine kinase inhibitors (TKIs). However, outcomes following stereotactic radiosurgery (SRS) for NSCLC BM patients with other pathogenic EGFR mutations and variants remain uncertain. We sought to characterize outcomes for NSCLC BM patients with pathogenic variants (PV) or variants of uncertain significance (VUS) in EGFR following SRS. We retrospectively identified 600 NSCLC BM patients who underwent an initial course of SRS during 2015- 2020. Demographic, clinical, genomic, and treatment characteristics were recorded. Intracranial progression-free survival (ICP-FS) and overall survival (OS) were estimated via the Kaplan Meier method. Median follow up was 9.6 months. 155 (25.8%) patients had actionable mutations, including in EGFR (112). Of those with EGFR mutations, next-generation sequencing (NGS) data was available for 65 patients. In patients with targetable EGFR mutations, 39 received pre-SRS and 69 received post-SRS treatment with a TKI, typically with a 1st/2nd generation TKI. Most patients (n=12/13) with EGFR VUS received (chemo)immunotherapy. OS was significantly better for patients with any EGFR mutation/variant compared to patients without a detected variant (median 21.1 mos vs 8.1 mos, p0.0001), however, there was no difference in ICP-FS. Patients with EGFR VUS had improved OS and ICP-FS compared to EGFR PVs (median 56.3 mos vs 19 mos, p=0.022) and (median 53.1 mos vs 7.7 mos, p=0.041), respectively. While patients with EGFR mutation/variants demonstrated improvement in OS, ICP-FS was likely limited by use of early generation TKIs with SRS. Notably, there was compelling improvement in OS and ICP-FS associated with EGFR VUS, which is hypothesis generating and requires a larger cohort for further examination.