Abstract B17: Health disparities in brain cancer incidence
Authors: Taioli Emanuela , Gan Wenqi , Riggins Gregory J. 
Published: May 2015

Abstract
Introduction: Glioblastoma Multiforme (GBM) is a lethal and highly aggressive cancer where risk factors, other than radiation exposure, are still largely unknown. It has been reported that US black patients have lower brain cancer rates than whites, and this has been ascribed to differences in socio-economic status. No study has analyzed possible risk factors that could explain the observed differences in rates with race.
Methods: All cases of pathologically confirmed GBM diagnosed between 1973 and 2010 were extracted from the Surveillance, Epidemiology and End Results (SEER) data base, and age-adjusted incidence rates x 100,000 persons were calculated according to race (blacks, whites, others), and age groups (0-19, 20-49, 50-85+ years). Survival was calculated using Cox proportional hazard models according to race. The NHANES data base was analyzed to assess time since last visit to a dentist (surveyed in 1999 through 2004), performance and frequency of a routine check-up in previous 3 years (surveyed in 1999 through 2002).
Results: There were 25,101 GBM patients in the data set, 360 of which were age 0-19 years, 4,234 age 20-49 years, 20,507 age 50-85+ years. GBM incidence rate was 0.1 x 100,000 persons in the younger age group, with no differences between black and white patients. Among patients age 20-49 years the incidence rate was 1.1 x 100,000 in whites and 0.7 x 100,000 in blacks, in patients age 50-85+ years the incidence rate was 9.5 x 100,000 and 4.4 x 100,000. The ratio of the incidence in white patients/black patients was 1, 1.6 and 2.2 respectively in the three age groups, without differences across geographic areas where the diagnosis was performed. Survival was similar in the two race groups: 3 year survival was 6.5% in whites, 9% in blacks; 5year survival was 3.8% and 4.7% respectively. Cancer treatment modalities did not significantly differ between the two races. From the NHANES data base (26,958 subjects, blacks = 6,719), 65.6 % of whites had a dentist visit within the previous year versus 54.3% of blacks (p=0.001). White subjects were significantly more likely to undergo routine check up once or more a year in comparison to black subjects (81.9% vs. 68.3%; p = 0.001).
Conclusions: GBM rates continue to be lower in black than white patients. The difference is largest in the older age group, suggesting a relation to the genetic background and subtype of GBM that occurs in patients older than 50 years and/or to environmental exposure. There is no geographic difference in cancer rates arguing against state specific environmental risk factors. Given the overlapping survival observed in black and white patients, it is unlikely that access to care plays a role in the differences in incidence rates. Racial differences in access to dental care and diagnostic radiation exposure should be explored in ad-hoc epidemiologic studies.
Citation Format: Emanuela Taioli, Wenqi Gan, Gregory J. Riggins. Health disparities in brain cancer incidence. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr B17. doi:10.1158/1538-7755.DISP13-B17