Demetrius Albanes

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NCI, DCEG

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PLCO (Learn more about this study)

2014-0020

Mar 7, 2014

Vitamin D, Vitamin D Binding Protein and Prostate Cancer Risk in African American Men

Experimental studies suggest a protective role of vitamin D in prostate carcinogenesis. Epidemiological data, however, do not support an inverse association between vitamin D status and prostate cancer risk. Black men have well-established higher prevalence of hypovitaminosis D, as well as elevated risk of prostate cancer relative to other racial/ethnic populations. Very little is known about the vitamin D-prostate cancer association in blacks because the overwhelming majority of studies of vitamin D and cancer to date have examined non-Hispanic white populations. In addition, emerging approaches for characterizing vitamin D status and evaluating vitamin D-cancer associations consider the role of vitamin D binding protein (DBP) carrier molecule parameters which may be informative for a more complete understanding of vitamin D metabolism and its role in cancer etiology.

Our primary aim is to examine the association between pre-diagnostic vitamin D status, including 25(OH)D, DBP and their molar ratio (a proxy for free or unbound vitamin D) and prostate cancer risk among black men. Our secondary aim is to characterize and compare vitamin D status between black and white men.

The proposed matched nested case-control study will use conditional logistic regression to estimate odds ratios (OR’s) and 95% confidence intervals for the association between vitamin D status and prostate cancer in black males. In addition, descriptive analyses will characterize vitamin D status using data from black and white participants randomized to the prostate cancer screening arm of the parent PLCO study.

Limited information exists on the association between vitamin D status and prostate cancer risk in blacks. Similarly, little is known about racial variation in vitamin D status beyond overall vitamin D concentrations. The PLCO cohort provides rich data that can examine this timely hypothesis specifically among black men using prospectively collected blood samples.

As a key part of my doctoral dissertation research studies, I will use these data to examine the following aims:

Aim 1: Determine whether vitamin D status (including total 25(OH)D, DBP, and the 25(OH)D:DBP molar ratio, a proxy for “free” or unbound 25(OH)D,[1,2]) is associated with prostate cancer risk in black men.

Aim 2: Determine whether there are interactions between DBP and 25(OH)D status and prostate cancer risk in black men. For example, DBP concentrations may moderate the association between circulating 25(OH)D and prostate cancer risk, and vice versa.[3]

Aim 3: Examine concentrations of total 25(OH)D and DBP and the 25(OH)D: DBP molar ratio among blacks and whites to evaluate racial variation in these characteristics.