Presentation (CTI)

OBJECTIVES: Glioblastoma (GBM) is an aggressive brain tumor with a poor prognosis. Previous observational studies have explored the association between metformin use and cancer outcomes, but findings have been inconsistent. This large population-based study aimed to evaluate the relationship between metformin exposure following GMB diagnosis and all-cause mortality.
METHODS: A retrospective cohort study was conducted utilizing the Surveillance, Epidemiology, and End Results (SEER) database linked with Medicare data. Patients 66 years and older diagnosed with GBM between January 1, 2007, and December 31, 2018, were included. Exclusion criteria were prior or subsequent diagnoses of other primary malignancies or GBM diagnosis by autopsy or death certificate. Time-dependent, covariate-adjusted mortality hazard ratios (HRs) for time-dependent metformin exposure (indicated after at least one metformin prescription following GBM diagnosis) were estimated using Cox regression models.
RESULTS: Among 16,069 patients diagnosed with GBM, 2,589 (16.1%) were exposed to metformin after diagnosis, and 8,964 (55.8%) died within 6 months of diagnosis. In the covariate-adjusted model, metformin exposure after GBM diagnosis was not associated with mortality hazard during the first three months of survival (HR=1.02; 95% CI: 0.91-1.14). Increased mortality was associated with patients exposed to metformin between three and nine months and beyond nine months post-GBM diagnosis (HR=1.22; 95% CI: 1.10-1.34 and HR=1.20; 95% CI: 1.09-1.14, respectively).
CONCLUSIONS: This large population-based study found no evidence of survival benefits associated with metformin exposure after GBM diagnosis. Further clinical trials are needed to clarify the potential impact of metformin on GBM survival outcomes.