Retrospective analysis of the impact of acid sphingomyelinase inhibiting drugs on survival of patients with glioblastoma

Purpose Glioblastoma (GBM) is the most common malignant primary brain tumor in adults and remains difficult to treat. Though still under investigation, acid sphingomyelinase (ASM) has been implicated in GBM lipid raft formation, which facilitates cancer signaling. We sought to verify if, and if so what kinds of ASM inhibitors (ASMis) improve outcomes in GBM. Methods We conducted a retrospective study of GBM patients treated between 2002 and 2024 at one academic center. ASMi impact on overall survival (OS) was assessed using Kaplan-Meier analysis and Cox proportional hazards models adjusting for age, sex, tumor location, use of tumor-treating fields (TTFs), and MGMT promoter methylation status. Propensity score matching was performed to account for baseline imbalances. Results ASMi use alone was not associated with a statistically significant OS benefit (HR = 0.80, 95% CI 0.55–1.2, p = 0.247). Stratifying by ASMi revealed fluoxetine as the only medication that significantly improved OS (HR = 0.35, 95% CI 0.14–0.88, p = 0.025). In a fluoxetine-only multivariate analysis (n = 20 vs. 186 controls), the survival benefit remained significant (HR = 0.29, 95% CI 0.11–0.73, p = 0.009). This effect persisted in the propensity-matched cohort (HR = 0.24, 95% CI 0.066–0.89, p = 0.033). Age and unmethylated MGMT promoter status were associated with decreased survival across multiple analyses. Conclusion Fluoxetine was independently associated with increased survival in GBM patients whereas ASMi use overall was not. These findings suggest that fluoxetine may have unique anti-tumor effects beyond ASM inhibition and justify further investigation.