Failure to complete standard radiation therapy in glioblastoma patients: Patterns from a national database with implications for survival and therapeutic decision making in older glioblastoma patients.
INTRODUCTION: It is estimated that 5%-10% of patients with newly diagnosed glioblastoma (GBM) fail to complete standard chemoradiation (CRT). We sought to determine the impact of failure to complete CRT on survival and to identify risk factors. METHODS: We queried the National Cancer Database and identified a cohort of 17,451 adults with GBM diagnosed from 2005 to 2012. The cohort was restricted to patients that started conventionally fractionated adjuvant chemoradiation of 1.8 to 2.0 Gy per fraction to a dose of ≤66Gy. Patients were stratified by RT dose: a) completed RT ≥ 58Gy, b) nearly completed RT ≥ 50Gy - <58Gy, and c) did not complete RT ≤ 50Gy. RESULTS: The CRT completion rate correlated with survival, 87% of patients completed CRT and had a median OS of 13.5 months, 4% were near completers (median OS 5.7 months), and 9% did not complete RT (median OS 1.9 months). Older age was associated with a higher risk of non-completion. Twenty-eight percent of patients ≥80 years old did not complete standard CRT (OR 2.99) and 19% of 70-79-year olds did not complete CRT (OR 1.99). The adjusted mortality hazard ratio was greater for patients that did not complete CRT across all age categories and for nearly complete CRT patients older than 40 (non-significant for age < 40). CONCLUSIONS: Failure to complete standard chemoradiation was associated with decreased survival in our cohort. Patients with risk factors for failure (like advanced age) should be considered for alternative treatments such as hypofractionated radiotherapy.