Abstract A29: Racial disparities in prostate cancer: Estimating the role of diet, lifestyle, and genetic factors among African-American and Caucasian-American men

Purpose: To assess the role of genetic and epidemiological risk factors in explaining racial disparities in prostate cancer incidence and mortality. Background: Black men are 1.6 times more likely to be diagnosed and 2.4 times more likely to die of prostate cancer than white men. An adequate explanation for these disparities remains elusive, as they have been shown to persist in equal care and equal access settings. Our group has previously shown associations between exposures of smoking, physical activity, body mass index (BMI) vitamin D level, coffee, lycopene, and genetic factors and risk of prostate cancer, particularly for lethal disease. We hypothesized that differences in the prevalence of these risk factors could explain a substantial proportion of the racial disparity in incident and lethal prostate cancer. Study Population: Our study utilized data on risk factor prevalence from the Health-Professionals Follow-Up Study (HPFS, N=51,529 men, 1986-2012) and the National Health and Nutrition Examination Study (NHANES III, 1988-1994), a nationally representative program of studies that gathers lifestyle and nutrition information. We used established relative risk estimates from the HPFS for the prostate cancer risk factors. Methods: To estimate the prostate cancer burden associated with these exposures, we calculated the population attributable fraction (PAF) for each risk factor by race. PAF can be defined as the reduction in incidence that would be achieved if the population had been entirely unexposed, compared with the current exposure pattern. We assumed that the risk ratio was the same among whites and blacks. To calculate the PAF, we used the prevalence of the exposure (risk factor) from the HPFS and NHANES III and crude and confounder-adjusted risk ratios from studies conducted in the HPFS cohort for each exposure and risk of lethal prostate cancer. We then calculated the difference in attributable risk between each race to estimate the reduction in lethal prostate cancer if black men had the same prevalence of risk factors as white men. Results: There were notable differences in risk factor prevalence by race. For example, black men had significantly lower levels of vitamin D, were less likely to drink coffee, and had a higher prevalence of obesity and smoking. The prevalence of several genetic loci for prostate cancer were also higher among black men. We estimated that if black men had the same prevalence of risk factors as white men, the percent reduction in prostate mortality was 18% for Vitamin D, 7% for obesity, 6% for genetic factors, 4% for coffee, 4% for current smoking, and 1% for lycopene. Conclusions: Certain lifestyle, dietary, and genetic factors are potentially responsible for a substantial proportion of the racial disparity in prostate cancer incidence and mortality. This important finding warrants further research and validation in additional cohorts, as our findings go beyond merely re-confirming that a racial disparity in prostate cancer persists: it suggests a strong underlying role for risk factors that could be addressed through prevention. The authors accept sole responsibility for all statements made in this abstract. Citation Format: Sam F. Peisch, Travis Gerke, Kathryn M. Wilson, Edward L. Giovannucci, Lisa B. Signorello, Lorelei A. Mucci. Racial disparities in prostate cancer: Estimating the role of diet, lifestyle, and genetic factors among African-American and Caucasian-American men. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr A29.