Abstract C41: Serum vitamin D and risk of prostate cancer among black men in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial
Authors: Layne Tracy M. , Weinstein Stephanie , Ma Xiaomei , Graubard Barry I. , Mayne Susan T. , Albanes Demetrius 
Published: May 2016

Introduction: Cohort studies and meta-analyses suggest higher circulating 25-hydroxyvitmain D (25(OH)D) is associated with increased prostate cancer risk. The association has largely been defined in non-Hispanic white populations. Using data from the PLCO Trial, we prospectively examined the association between circulating 25(OH)D and prostate cancer risk in black men, a group with lower circulating vitamin D and higher prostate cancer rates relative to other racial/ethnic groups.

Methods: This nested case-control analysis included 226 black prostate cancer cases and 452 controls matched 2:1 based on age at randomization (+/- 5 years), date of blood draw (+/- 30 days), and calendar-year of entry into the cohort. Serum 25(OH)D was measured using liquid chromatography-mass spectrometry (LC/MS), and we estimated odds ratios (OR) and 95% confidence intervals (CI) for prostate cancer by quartiles and clinically defined cut-points (&lt;25, 25-50, and 75+, with 50-&lt;75 nmol/L as the referent group) of baseline 25(OH)D from multivariable conditional logistic regression models. Two methods were used to adjust for seasonal variation in 25(OH)D: 1) quartiles created for sunnier (May-October) and darker (November-April) months were combined to create season-specific quartiles; 2) 25(OH)D was regressed on week of blood draw and the residuals were used to create season-standardized quartiles. Risk of total, aggressive (clinical stage III or IV or Gleason score ≥7) and non-aggressive (clinical stage I or II and Gleason score &lt;7) disease were determined.

Results: We found statistically non-significant associations between circulating 25(OH)D and risk of total prostate cancer in black men (season-specific Q4 vs. Q1 OR=0.83, 95% CI:0.42-1.67, P for trend = 0.41). For non-aggressive disease, the association was inverse (global P-value = 0.025), particularly in the 3rd quartile: Q3 vs. Q1 OR= 0.17, 95% CI: 0.06-0.55, Q4 vs. Q1 OR= 0.62, 95% CI: 0.23-1.71, P for trend =0.10). In contrast, the association with aggressive disease, while non-significant, appeared positive (Q4 vs. Q1 OR=1.18, 95% CI: 0.38-3.62, P for trend = 0.77). Similar results were obtained for total, non-aggressive, and aggressive prostate cancer using season-standardized quartiles of 25(OH)D. There was no evidence of an association with total prostate cancer using clinically defined cut-points, although categories above and below the referent category appeared to be inversely associated with risk of aggressive disease, while positively associated with risk of non-aggressive disease. We found no evidence of a difference in our findings for total prostate cancer and 25(OH)D when stratified by median total vitamin D intake, family history of prostate cancer, smoking status, physical activity, aspirin use, or body mass index.

Conclusions: Our analysis of circulating 25(OH)D and prostate cancer risk among black men indicates a possible modest inverse association with total prostate cancer risk. This was reflective of the association with non-aggressive disease, where circulating 25(OH)D had a protective effect, but not for aggressive disease. Our finding of potential variability in the vitamin D-prostate cancer risk association by disease aggressiveness may be related to differences in pathogenesis and prognosis of indolent and aggressive prostate cancers. Our study adds to the limited prospective research addressing this relationship in a high risk population. Additional studies of the vitamin D-prostate cancer risk association in black men are needed.

Citation Format: Tracy M. Layne, Stephanie Weinstein, Xiaomei Ma, Barry I. Graubard, Susan T. Mayne, Demetrius Albanes. Serum vitamin D and risk of prostate cancer among black men in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C41.