385 Genomic Alterations Associated With Postoperative Nodular Leptomeningeal Disease After Resection of Brain Metastases

INTRODUCTION: The relationship between brain metastasis resection and risk of nodular leptomeningeal disease (nLMD) is unclear. Prior studies have not explored genomic alterations associated with postoperative nLMD. METHODS: A retrospective, single-center study was conducted with patients who underwent resection of a BM with available clinical and genomic data available. Postoperative nLMD was the primary endpoint of interest. Targeted next-generation sequencing of over 500 oncogenes using a CLIA certified assay was performed in brain metastases. Cox proportional hazards analyses were performed to identify clinical features and genomic alterations associated with nLMD. RESULTS: One hundred and one patients composed the cohort with tumors originating from multiple cancer types. There were 15 cases of nLMD (14.9% of the cohort) with a median time from surgery to nLMD diagnosis of 8.2 months. Two supervised machine learning algorithms consistently identified CDKN2A/B co-deletion and ERBB2 amplification as the top predictors associated with postoperative nLMD across all cancer types. In a multivariate Cox proportional hazard analysis including clinical factors and genomic alterations observed in the cohort, tumor volume (HR 8.8, 95% CI 1.1-69, p = 0.04), CDKN2A/B co-deletion (HR 5.3, 95% CI 1.7-16.9, p = 0.004), and ERBB2 amplification (HR 3.9, 95% CI 1.1-14.4, p = 0.04) were associated with decreased time to postoperative nLMD. CONCLUSIONS: In addition to increased resected tumor volume, ERBB2 amplification and CDKN2A/B deletion were independently associated with an increased risk of postoperative nLMD across multiple cancer types. Additional work is needed to determine if targeted therapy decreases this risk in the postoperative setting.