Abstract B69: Effects of obesity and neighborhood socioeconomic status on prostate cancer stage and grade
Authors: Zeigler-Johnson Charnita M. , Liu Ziyue , Spangler Elaine , Rebbeck Timothy 
Published: December 2010

Background: Obesity has been shown to increase the risk for advanced prostate cancer. Although linked to both obesity and advanced cancer, neighborhood socioeconomic status (SES) has not been studied as a modifier of obesity effects in prostate cancer patients. Ethnic differences in obesity among men are less pronounced in lower SES environments. It is possible that the relationship between obesity and prostate cancer outcomes varies by neighborhood characteristics.

Objective: The goal of this project was to study neighborhood SES as an effect modifier of obesity on prostate cancer characteristics. Neighborhood SES differences may help to explain ethnic differences observed in prostate cancer outcomes. Our general hypotheses are that (1) neighborhood SES differs for African-American and European American prostate cancer patients recruited from the same medical center and (2) neighborhood SES modifies the effects of obesity on prostate cancer outcomes.

Methods: A case-case design was proposed to examine the relationship between neighborhood SES and prostate cancer severity. The residential addresses of prostate cancer patients from the University of Pennsylvania were geocoded. Census tract data was downloaded from the Census Bureau website and merged with patient data. Obesity was defined as a Body Mass Index (BMI) ≥30 kg/m2 and non-obese as BMI &lt;30 kg/m2. Median cut-points for census tract variables were determined for all patients combined. Census tract variables included per capita income, percent poverty, median household income, education and employment. Outcomes for this study included tumor stage and tumor grade. Age-adjusted multivariate models were used to examine obesity effects on stage and grade stratified by neighborhood SES. Analyses were stratified by ethnicity.

Results: 1000 European American and 144 African-American prostate cancer patients were included in these analyses. We observed no ethnic differences in patient-level variables except for those related to obesity. The African-American sample had a higher mean BMI (29 vs. 27 kg/m,2 p=0.001) compared to European Americans. Neighborhood SES characterized by below median census tract income and education was more prevalent among African-Americans. (&lt;0.001) There was no difference in stage at diagnosis by obesity status for African-Americans or European Americans. However, odds ratios increased to significance among men in either group who lived in neighborhoods below median SES characteristics (i.e., below median per capita income: OR=2.60, 95% CI=1.06-6.36 for African Americans; OR=1.77, 95% CI=1.14-2.76 for European Americans). Obesity was associated with tumor grade at baseline in European Americans (OR=1.52, 1.09-2.11). Stratification by neighborhood SES demonstrated general associations of obesity on tumor grade for European Americans.

Conclusions: Lower neighborhood SES is more common among African-American prostate cancer patients than European American cases. The relationship between obesity and tumor stage may be influenced by lower neighborhood SES. Modification of obesity effects by neighborhood SES may suggest strategies for prostate cancer intervention in high-risk communities.

Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B69.