Comparison of intracerebrospinal fluid methotrexate by Ommaya reservoir versus lumbar puncture in leptomeningeal carcinomatosis with hydrocephalus: a retrospective cohort study.

BACKGROUND: Leptomeningeal carcinomatosis (LC) complicated by hydrocephalus carries a poor prognosis. Intracerebrospinal fluid (intra-CSF) chemotherapy is a main treatment, but the optimal route of administration remains unclear. METHODS: This retrospective cohort study included 36 LC patients with hydrocephalus who received intra-CSF methotrexate via Ommaya reservoir (OR, n = 15) or lumbar puncture (LP, n = 21). Efficacy, safety, and overall survival (OS) were compared. Prognostic factors were analyzed using Cox regression. RESULTS: The OR group achieved significantly higher overall response rate (86.7% vs. 47.6%, p = 0.016) and clinical response rate (100% vs. 52.4%, p = 0.002), alongside superior intracranial pressure relief (p = 0.042). Rates of complications and chemotherapy-related toxicities were comparable in both arms. Median overall survival (OS) was 54.7 weeks for OR patients versus 44.1 weeks for LP patients, without statistically significant intergroup difference (p = 0.53). After adjusting for primary tumor subtypes in multivariate Cox regression, extraneural metastasis remained an independent adverse prognostic factor (HR = 4.251, p = 0.009), whereas targeted therapy independently predicted prolonged OS (HR = 0.101, p < 0.001). Treatment response lost independent predictive significance after full adjustment (p = 0.055). Tumor subtype showed no significant correlation with survival outcomes. CONCLUSION: In LC patients with hydrocephalus, intra-CSF methotrexate via OR does not prolong OS but yields superior symptom relief and intracranial pressure control without increased adverse events. Concurrent targeted therapy is independently linked to favorable long-term survival; extraneural metastasis confers higher mortality risk.