Intrathecal chemotherapy via Ommaya reservoir improves survival in leptomeningeal metastasis

BACKGROUND: Leptomeningeal metastasis (LM) is a lethal complication of advanced malignancy with limited therapeutic options and poor survival. Intrathecal chemotherapy represents a standard treatment for LM and can be administered via repeated lumbar puncture (LP) or an intraventricular Ommaya reservoir. However, the comparative efficacy and safety of these two administration routes remain unclear. This study aims to compare the clinical outcomes of intrathecal chemotherapy delivered by Ommaya reservoir versus LP in patients with LM, and to provide further evidence for clarifying the advantages of the Ommaya reservoir in clinical practice. METHODS: We systematically searched PubMed, Embase and Web of Science for relevant studies published between 1986 and 2026. Studies directly comparing intrathecal chemotherapy delivered via Ommaya reservoir and LP were included in the meta-analysis. Disease control rate (DCR) was pooled as odds ratios (OR) using a random-effects Mantel-Haenszel model to account for between-study heterogeneity, and overall survival (OS) was pooled as hazard ratios (HR) using the inverse-variance method. Because adverse events (AEs) were incompletely reported in comparative studies, an additional safety analysis including single-arm cohorts was conducted using a binomial generalized linear mixed model (GLMM) with a logit link. Risk of bias was assessed using the ROBINS-I tool. RESULTS: A total of four comparative studies with a moderate overall risk of bias were included in our meta-analysis. Three studies contributed data on DCR, and three studies contributed data on OS. The pooled analysis showed no significant difference in DCR between the Ommaya and LP groups (OR 2.03; 95% CI 0.53-7.78, p = 0.30), with moderate heterogeneity (I² = 66%). In contrast, Ommaya-based intraventricular delivery was associated with significantly improved OS compared with LP (HR 0.39; 95% CI, 0.25-0.61, p < 0.0001), with no significant heterogeneity (I² = 0%). In the exploratory safety analysis of six single-arm cohorts, the estimated probability of overall AEs was numerically lower in the Ommaya group (OR 0.43; 95% CI, 0.21-0.87, p = 0.0191). While this finding is derived from non-comparative data and should be treated cautiously, it offers valuable insight into safety profile. CONCLUSION: Ommaya reservoir-based intraventricular administration of intrathecal chemotherapy may provide a survival advantage over LP in patients with LM, while demonstrating a generally acceptable and manageable safety profile. Further comparative studies with standardized response criteria and rigorous safety reporting are warranted.