Adult cerebellar glioblastoma: understanding survival and prognostic factors using a population-based database from 1973 to 2009

Abstract

Objective: Glioblastoma (GB) is rarely found in the cerebellum. Because of its rarity, it is poorly understood if cerebellar GB (CGB) behaves similarly to supratentorial GB. Studies have been limited to case reports and small case series. A better understanding of CGB may help guide treatment strategies.

Methods: Surveillance, Epidemiology and End Results database was analyzed from 1973 to 2009 for all adult patients with GB located in the cerebellum. Stepwise multivariate proportional hazards regression analyses were used to identify factors independently associated with survival.

Results: Two hundred eight (0.9%) patients with CGB were identified from 23,329 GB patients with known locality. The mean age was 58 years. Median survival was 8 months, with 1-, 2- and 5-year survival rates of 21%, 13%, and 2%. When compared to supratentorial GB, CGB occurred in younger patients (58 ± 16 vs. 61 ± 13 years, P = 0.001), less commonly in Whites (85.6% vs. 91.3%, P = 0.005), and were smaller (3.7 ± 1.1 vs. 4.5 ± 1.7 cm, P = 0.001). A cerebellar location independently predicted poorer survival when compared to other GB locations (P = 0.048). In multivariate analysis for patients with CGB, younger age (P < 0.001), Asian or Pacific Islander race (P = 0.046), and radiation therapy (P < 0.001) were independently associated with prolonged survival.

Conclusion: CGBs are difficult to analyze using institutional series because of their rarity. This study shows they are clinically different from supratentorial GB. Among patients with CGB, radiation therapy may prolong survival. This may help guide treatment strategies aimed at prolonging survival for patients with these extremely rare lesions.

Keywords: CGB; Cerebellar; Cerebellar glioblastoma; Cerebellum; GB; GTR; Glioblastoma; Glioma; Gross total resection; ICD-O; International Classification of Disease for Oncology; SEER; STGB; Supratentorial glioblastoma; Surveillance, Epidemiology and End Results; Survival.

Figure 1

Kaplan-Meier plots of survival for the entire cohort of adult patients with cerebellar glioblastoma (CGB) and supratentorial glioblastoma (STGB). Median survival for CGB was 8 months, and 1-, 2-, 5-year survival rates were 21%, 13%, and 2%, respectively. STGB demonstrated median survival of 9 months, with 1-, 2-, and 5-year survival rates of 12%, 7%, and 1%, respectively. The survival difference observed in these 2 groups did not reach statistical significance (P = 0.143). However, only after adjusting for the stratification variables in a multivariate analysis, there was evidence of a survival difference between the two groups in favor of CGB (P = 0.048).

Figure 2

Kaplan-Meier plots of survival for the entire cohort of adult patients with cerebellar glioblastoma (CGB) stratified by age groups at diagnosis. Median survival for the <40, 40–49, 50–59, 60–69, and ≥70 group was 17, 23, 10, 4, and 4 months, respectively. Survival decreased among CGB patients as age advances. Patients in the 50–59, 60–69, and ≥70 group were statistically different from the <40 group (P = 0.035, P = 0.004, and P < 0.001).

Figure 3

Kaplan-Meier plots of survival for the entire cohort of adult patients with cerebellar glioblastoma (CGB) stratified by extent of resection. Median survival for the no-surgery (NS), biopsy (Bx), partial resection (PR), and gross total resection (GTR) group was 4, 7, 6, and 16 months, respectively. When compared to the NS group, only the GTR group was statistically different (P = 0.003).

Figure 4

Kaplan-Meier plots of survival for the entire cohort of adult patients with cerebellar glioblastoma (CGB) stratified by the use of radiotherapy. Median survival for the radiation group was 11 months, and 2 months for the no-radiation group (P < 0.001).