Survival outcomes and prognostic factors of infratentorial glioblastoma in the elderly.

Introduction: Infratentorial glioblastoma(itGBM) is a rare and rapidly progressive form of GBM with poor prognosis. However, no studies have adequately examined itGBM outcomes in elderly patients (>65 years). Here, we used a national database to fill this knowledge gap.

Methods: SEER 18 registries were utilized to identify adult itGBM patients diagnosed between 2000-2016. itGBM cases were further divided into cerebellar and brainstem GBM as cGBM and bGBM, respectively. Kaplan-Meier analysis and Cox hazards proportional regression models were performed to assess factors associated with overall survival (OS).

Results: Among 137 (33%) elderly patients from the study cohort (N = 420), median age was 74 years, 38% were female, and 85% were white. Median OS in elderly itGBM patients was shorter than younger adults (10 vs. 5-months, p < 0.001). Multivariate analysis by tumor location revealed that older age was associated with poor survival for cGBM, but not for bGBM. Gross-total resection (GTR) was associated with better outcomes for both cGBM and bGBM. Radiotherapy had survival benefits for cGBM; meanwhile, chemotherapy prolonged OS in bGBM. In the elderly, advanced age (80 + years) was associated with poor outcomes, while GTR, CT and RT were all associated with improved survival.

Conclusions: In our study, while elderly patients had worse survival compared to younger adults for both cGBM and bGBM, GTR improved OS in elderly itGBM, with CT and RT exhibiting a location-dependent survival benefit. Thus, elderly itGBM patients should undergo a combination of maximal resection and adjuvant treatment guided by infratentorial tumor location for maximal survival benefit.