Vitamin D deficiency was an indicator of aggressive prostate cancer and spread of the disease in European American and African American men who underwent their first prostate biopsy because of abnormal prostate-specific antigen (PSA) test and/or digital rectal examination (DRE) results, according to a new study.
“Vitamin D is a steroid hormone that is known to affect the growth and differentiation of benign and malignant prostate cells in prostate cell lines and in animal models of prostate cancer,” said lead author Adam B. Murphy, MD, MBA, assistant professor in the Department of Urology at the Northwestern University Feinberg School of Medicine in Chicago, Illinois. “In our study, vitamin D deficiency seemed to be a predictor of aggressive forms of prostate cancer diagnosis in European American and African American men.
“The stronger associations in African American men imply that vitamin D deficiency is a bigger contributor to prostate cancer in African American men compared with European American men,” added Murphy. “Vitamin D supplementation may be a relevant strategy for preventing prostate cancer incidence and/or tumor progression in prostate cancer patients.”
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The most accurate way to measure how much vitamin D we have in our body is to measure levels of 25-hydroxyvitamin D (25-OH D) in our blood. The normal range of 25-OH D is 30 to 80 ng/mL.
In this study, European American and African American men had 3.66 times and 4.89 times increased odds of having aggressive prostate cancer (Gleason grade of 4+4 or higher), respectively, and 2.42 times and 4.22 times increased odds of having tumor stage T2b or higher, respectively, if their 25-OH D levels were less than 12 ng/mL at the time of prostate biopsy. In addition, African American men had 2.43 times increased odds of having prostate cancer, if their 25-OH D levels were less than 20 ng/mL.
Between 2009 and 2013, Murphy and colleagues enrolled 667 men, age 40 to 79 years, who were undergoing their first prostate biopsy at 1 of 5 urology clinics in Chicago following an abnormal PSA or DRE. Serum 25-OH D levels were measured at recruitment. Of the study participants, 273 were African American and 275 were European American, and 168 men from each group had a prostate cancer diagnosis from their biopsy. The study was published in Clinical Cancer Research (2014; doi:10.1158/1078-0432.CCR-13-3085).
The researchers found that the mean 25-OH D levels were significantly lower among African American men (16.7 ng/mL) compared with European American men (19.3 ng/mL). The highest 25-OH D level was 71 ng/mL in European American men, whereas it was only 45 ng/mL in African American men.
They found a dose-response relationship between tumor grade and vitamin D level for both European American and African American men, and the association held true even after adjusting for potential confounders including diet, smoking habits, obesity, family history, and calcium intake. Skin color, which determines cumulative vitamin D levels from exposure to sun, may partly explain the discrepancies observed between European American and African American men, explained Murphy.
