Introduction: It is unclear whether the survival difference observed between glioblastoma (GBM), giant cell glioblastoma (gcGBM), and gliosarcoma (GSM) patients is due to differences in tumor histology, patient demographics, and/or treatment regimens.

Methods: The National Cancer Database (NCDB) was utilized to evaluate patients diagnosed with GBM, gcGBM, and GSM between 1998 and 2011. Kaplan-Meier survival estimates and Cox proportional hazards models were utilized to estimate overall survival (OS).

Results: A cohort of 69,935 patients was analyzed; 67,509 (96.5%) of these cases had GBM, 592 (0.9%) gcGBM, and 1,834 (2.6%) GSM. The median age for GBM and GSM patients was 61 versus 51 years for gcGBM (p<.0001). Higher levels of resection (p<.0001) and radiation (p=.001) were observed in gcGBM patients compared to other histologies. Multivariate analysis showed that gcGBM patients had a 20% reduction in the hazards of mortality (HR 0.80, 95% CI: 0.69-.93) compared to GBM, while GSM patients had higher hazards of mortality (HR 1.04, 95% CI: 0.96-1.12) than the GBM cohort.

Conclusions: Previous studies have suggested a disparity in the survival of patients with glioblastoma tumors and their histological variants. Using a large cohort of patients treated at hospitals nationwide, this study found a 20% reduction in the hazards of mortality in gcGBM patients compared to GBM. Similarly, gcGBM patients had a 24% reduction in the hazards of mortality compared to the GSM cohort. Gliosarcoma patients had a 3% increase in the hazards of mortality compared to GBM.

Patient Care: Through an appreciation of the relative survival of common GBM subtypes discovered through this population-based analysis, providers will be able to give patients with a GBM subtype a better assessment of their overall survival relative to classic GBM patients. Additionally for patients with a known aggressive subtype of GBM, such as gliosarcoma, this work may prompt more aggressive adjuvant therapy regimens as a means to combat this more aggressive histological subtype.

Learning Objectives: By the conclusion of this session, participants should be able to: 1. Define clinically relevant histological variants of glioblastoma. 2. Understand the variable harzards of mortality in these sub-types of glioblastoma multiforme, including the relatively improved survival of gcGBM patients and the relatively worse survival of GSM patients.

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