Prognostic value of the Evans index in neoplastic meningitis: a real-world cohort study.

PURPOSE: Neoplastic meningitis (NM) from solid tumors is associated with a grim outcome. The Evans Index (EI) has recently been proposed as a prognostic imaging biomarker in these patients, but external validation is lacking. We aimed to independently validate its prognostic performance in one of the largest real-world cohorts reported to date. METHODS: Information from patients with NM seen from January 2010 to December 2024 at a single center with an imaging study available for review was retrospectively analyzed. Multivariable adjustments were made to measure the association between EI and overall survival (OS). RESULTS: A total of 345 patients were included; the most prevalent primary tumors were breast (66%), lung (12%), genitourinary (6%), and head and neck (5%). The median OS (MOS) of the whole cohort was 6.9 months (95% CI, 5.5 to 8.3); the MOS for those with EI ≤ 0.3 was 7.36 months, compared with 2.99 months for those with EI > 0.3 (P = .020). After adjusting for age, sex, primary tumor, Karnofsky Performance Score (KPS), symptoms, extracranial disease activity, CSF protein, and CSF lactic dehydrogenase levels, the EI was significantly associated with mortality (EI > 0.3: HR 1.95 [95% CI, 1.09-3.50], P = .024). CONCLUSION: In this validation study, the baseline EI was associated with prognosis even after adjustment for confounding factors. The EI may have clinical utility in assessing outcomes in patients with NM.