Abstract A72: Occupational sunlight exposure, race, and risk of renal cancer

Abstract

Abstract Introduction: Vitamin D, obtained primarily from ultraviolet (UV) exposure, is hydroxylated to its biologically active form within the kidneys. Epidemiological evidence supporting a relationship between vitamin D and kidney cancer risk has been inconsistent despite experimental data indicating that vitamin D and its metabolites may inhibit carcinogenesis. Previously we reported an inverse association between renal cell carcinoma (RCC) risk and occupational UV exposure among men in Europe. In the current study, we examined the association between occupational UV exposure and RCC risk among U.S. residents and investigated whether this association varies by race and sex. Methods: Lifetime occupational data for 1,217 RCC cases and 1,235 controls in a large population-based case-control study were blindly assessed by an industrial hygiene expert to create a job exposure matrix that categorized frequency, duration, confidence, and intensity of occupational UV exposure. Categorical exposure metrics used to evaluate exposure-response relationships with occupational exposure were based on tertiles of exposure levels among controls. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) to examine the association between RCC risk and UV exposure by sex and race. Results: Across all exposure-response matrices, women in the highest tertile of occupational UV exposure had a 40% reduction in RCC risk compared to those in the lowest tertile; risk decreased significantly as occupational UV exposure increased (p-trend=0.01 to 0.004). A marginally significant, non-linear inverse association was observed among men. Further stratification by race revealed similar findings for black and white women. Significantly decreased associations between RCC risk and occupational UV exposure were observed among black men (p-trend=0.05), but not among white men, although results for blacks were based on small numbers. Our findings suggest that occupational UV exposure may protect against RCC. We caution any inferences made using race, given power limitations for stratified analyses, until additional well-powered studies can replicate and extend these findings. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A72.