SURG-08: SUPERIOR EFFICACY OF GROSS TOTAL RESECTION IN ANAPLASTIC ASTROCYTOMA PATIENTS RELATIVE TO GLIOBLASTOMA PATIENTS

INTRODUCTION: Because of their relative rarity, Anaplastic Astrocytomas (AA, or WHO grade III astrocytoma) are often grouped with glioblastomas in investigative studies and clinical treatment paradigms. However, there are many reasons to expect that the biology and therapeutic response of AAs may differ from those of glioblastoma. Here, we examined the clinical benefit of gross total resection (GTR) and temozolomide in AA patients relative to those suffering from glioblastoma (WHO grade IV). METHODS: Using the Surveillance, Epidemiology and End Results (SEER) database, we identified 2,755 grade III and 21,962 grade IV gliomas between 1999 and 2010. Surgical resection was defined as GTR and subtotal resection (STR). Kaplan-Meier, multivariate Cox regression, and Wald's statistics were used to assess overall survival. RESULTS: The hazard of dying from the AA was reduced in GTR patients by 38% (CI: 33%-48%) relative to STR patients. This reduction is approximately doubled relative to that observed in glioblastoma where GTR was associated only with a 20% reduction relative to STR (p < 0.0001). The AA patients who most benefit from GTR were age < 50 treated in the post-temozolomide era (2005-2010). In this population, GTR was associated with a 66% reduction in the hazard of dying from the disease (CI: 43%-81%), translating to >36 months gain in median survival. This reduction represents a ten-fold increase relative to that observed in glioblastoma, where GTR was only associated with a 6.8% risk reduction in risk of death relative to STR patients (p< 0.001) and a 6 months gain in median survival. CONCLUSION: The SEER data suggest that the overall survival benefit associated with GTR relative to STR was notably greater for AA patients age <50 treated in the post-temozolomide era relative to glioblastoma patients. These results provide the foundation for cost-benefit analysis during surgical decision-making in the treatment AA patients.