Abstract LB-12: Plasma 25-hydroxyvitamin D levels are associated with aggressive prostate cancer among African Americans in the North Carolina-Louisiana Prostate Cancer Project (PCaP).

Abstract

Abstract Background: Experimental and ecological studies support links between vitamin D and prostate cancer prevention and prognosis. Given the lower levels of circulating 25-hydroxyvitamin D [25(OH)D] and higher prostate cancer incidence and mortality among African Americans compared to other racial/ethnic groups, the aim of this investigation was to examine the relationship between plasma 25(OH)D levels and prostate cancer aggressiveness among African and European Americans. Methods: Plasma 25(OH)D was measured using LC/MS/MS in 537 African Americans and 663 European Americans with newly-diagnosed prostate cancer from PCaP. Men were classified as cases (high aggressiveness) if Gleason sum ≥8, or PSA >20 ng/ml, or Gleason sum ≥7 AND clinical stage = T3c-T4c, or Gleason sum=7 with primary pattern 4. The comparison group (low aggressiveness) included men with Gleason sum <7 AND Stage T1-T2 AND PSA < 9 ng/ml. Plasma 25(OH)D was categorized into tertiles in each race based on distributions among the comparison groups. Odds ratios (OR) and 95% confidence intervals (95%CI) were calculated for cases by tertile of plasma 25(OH)D using logistic regression with adjustment for potential confounders. Results: African Americans had significantly lower mean concentrations of 25(OH)D (17.7 ± 7.6 ng/ml) compared to European Americans (24.6 ± 9.6 ng/ml). The highest tertile (mean=25.79 ng/ml & median=24.29 ng/ml) and middle tertile (mean=16.09 ng/ml & median=15.83) of plasma 25(OH)D were positively associated with highly aggressive prostate cancer among African Americans after adjustment for age, season, education, physical activity, smoking status, and PSA screening history (OR=1.7, 95% CI=1.0, 2.8 and OR=1.8, 95%CI=1.1, 3.0, respectively). No significant associations were observed for European American men. Conclusions: Plasma 25(OH)D was positively associated with prostate cancer aggressiveness among African Americans but not European Americans, such that subjects with highly aggressive prostate cancer had increased odds of having higher plasma 25(OH)D levels. Research samples were collected after diagnosis, so effects of treatment, extent of disease or associated processes (e.g. weight loss) on plasma 25(OH)D may explain the findings. Ongoing studies include analysis of vitamin D binding protein (DBP) in the plasma and genotyping of DBP affinity variants in PCaP subjects. This approach may help explain the racial differences found, since DBP may modulate the impact of vitamin D status on prostate cancer. Citation Format: Anna Woloszynska-Read, Lenore Arab, John Adams, Jeannette T. Bensen, Elizabeth TH Fontham, James L. Mohler, Joseph Su, Fred Tabung, Hongmei Zhang, Donald L. Trump, Candace S. Johnson, Susan E. Steck. Plasma 25-hydroxyvitamin D levels are associated with aggressive prostate cancer among African Americans in the North Carolina-Louisiana Prostate Cancer Project (PCaP). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-12. doi:10.1158/1538-7445.AM2013-LB-12