title: Underutilization of radiation therapy in patients with glioblastoma: predictive factors and outcomes.
abstract: BACKGROUND
  Randomized trials have demonstrated that radiation improves survival in patients with glioblastoma. The purpose of this study was to characterize the risk factors and impact of omission of radiation therapy in such patients.
  
  
  METHODS
  The Surveillance, Epidemiology, and End Results (SEER) program was used to identify 22,777 patients diagnosed with glioblastoma between 1988 and 2007. Multivariable logistic regression was employed to identify predictors associated with omission of radiation. Cox regression was used to characterize the impact of omitting radiation on all-cause mortality.
  
  
  RESULTS
  Among the entire cohort, 16,863 of 22,777 patients (74%) received radiation, whereas 5914 of 22,777 patients (26%) did not. Factors associated with omission of radiation included older age (OR=1.048 per year increase, 95% CI=1.046-1.051, P<.001), lower annual income (OR=0.93 per $10,000 increase, 95% CI=0.90-0.96, P<.001), African American race (reference=white, OR=1.19, 95% CI=1.03-1.37, P=.02), Hispanic race (OR=1.34, 95% CI=1.19-1.50, P< .001), Asian American race (OR=1.24, 95% CI=1.04-1.48, P<.001), unmarried status (OR=1.71, 95% CI=1.60-1.83, P< .001), and subtotal resection/biopsy (OR=1.82, 95% CI=1.69-1.96, P<.001). The use of radiation was significantly associated with improved overall survival (2-year survival: 14.6% versus 4.2%, P<.001; adjusted HR=2.09, 95% CI=2.02-2.16, P<.001). When the population was restricted to patients <50 years old, these findings remained largely unchanged.
  
  
  CONCLUSIONS
  Radiation therapy is associated with survival benefit in patients with glioblastoma, and sociodemographic factors play a significant role in the underutilization of radiation. The underlying causes for these disparities in care require further research.
authors.affiliation: Harvard Radiation Oncology Program, Boston, Massachusetts.
authors.forename: Ayal A
authors.initials: AA
authors.lastname: Aizer
authors.forename: Marek
authors.initials: M
authors.lastname: Ancukiewicz
authors.forename: Paul L
authors.initials: PL
authors.lastname: Nguyen
authors.forename: Helen A
authors.initials: HA
authors.lastname: Shih
authors.forename: Jay S
authors.initials: JS
authors.lastname: Loeffler
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Oh
mesh_terms: D001741:Black or African American; D000368:Aged; D001213:Asian; D016543:Central Nervous System Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D005260:Female; D005909:Glioblastoma / Q000401:mortality* / Q000532:radiotherapy*; D006630:Hispanic or Latino; D006801:Humans; D007182:Income; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011878:Radiotherapy / Q000706:statistics & numerical data*; D012307:Risk Factors; D018426:SEER Program; D012959:Socioeconomic Factors; D016019:Survival Analysis
keywords: glioblastoma; omission; radiation; risk factors; survival