Fate of Brain Metastasis With Cerebrospinal Fluid Space Invasion Based on MRI Findings: Clinical Features and Factors Affecting Progression to Overt Leptomeningeal Metastasis.

backgroundParenchymal brain metastasis (BM) and its extended growth into cerebrospinal fluid (CSF) pathways or surgical spillage could result in leptomeningeal metastasis (LM). We defined BM with epipial spread or dural attachment on MRI as BM with CSF space invasion (BM-CSFi), regardless of CSF cytology results, and evaluated its clinical course after BM resection.

methodsWe retrospectively reviewed 297 patients who underwent craniotomy for BM excluding patients followed for <6 months or without follow-up MRI. Primary outcomes were proportion of patients progressing to overt LM and time to progression. We also evaluated clinical and radiologic variables to identify risk factors for LM progression.

resultsA total of 91 patients (30.6%) developed overt LM, with median time to progression of 7.9 months during 18.3 months follow-up after the craniotomy. On multivariable analysis, preoperative MRI evidence of dural attachment with enhancement (hazard ratio [HR], 5.59;

conclusionBM-CSFi, defined by preoperative MRI findings, may represent a clinically important precursor of LM. Our findings highlight the need for close monitoring of patients with BM-CSFi and the development of management protocols to minimize the risk of LM progression.