Vitamin D deficiency predicts prostate biopsy outcomes

By Joanna Lyford, Senior medwireNews Reporter

Men with vitamin D deficiency are more likely than men with normal levels to test positive for prostate cancer on biopsy, and to have aggressive disease, US researchers have found.

The strength of the associations varied by race, suggesting that low levels of vitamin D play a greater role in the development of prostate cancer in men of African rather than European heritage, say the study authors.

“Our work supports the hypothesis that 25-hydroxyvitamin D is a potential biomarker that plays a clinically significant role in prostate cancer, and it may be a useful modifiable risk factor in the disease”, write Adam Murphy (Northwestern University, Chicago, Illinois) and co-authors in Clinical Cancer Research.

“Additionally, differences in serum 25-hydroxyvitamin D levels may explain ethnic disparities in prostate cancer–specific incidence, morbidity, and mortality.”

The study included 667 men aged 40 to 79 years who were referred for prostate biopsy based on an abnormal prostate-specific antigen blood test and/or digital rectal examination.

Biopsy results were positive for prostate cancer in 383 men (cases) and negative in 284 (controls). Mean vitamin D levels were similar between cases and controls (21.0 and 22.0 ng/mL) and the prevalence of vitamin D deficiency (defined as serum 25-hydroxyvitamin D <20 ng/mL) did not significantly differ between groups, at 43.7% in cases and 37.8% in controls.

Interestingly, the highest recorded vitamin D level was much higher in European-American men than in African Americans, at 71.0 versus 45.0 ng/mL.

Within the subgroup of African-American men, mean vitamin D levels were significantly lower in cases than controls (16.7 vs 19.3 ng/mL). In multivariate analysis, vitamin D deficiency was a significant independent predictor of prostate cancer diagnosis on biopsy, with an odds ratio of 2.43.

Vitamin D deficiency was also associated with more aggressive prostate cancer – irrespective of race. The risk of having a tumour with a Gleason score of 4+4 or higher was increased 3.66-fold in European-American, and 4.89-fold in African-American men with a deficiency, versus those with higher levels.

A similar pattern was seen for clinical tumour stage and National Comprehensive Cancer Network risk category, both of which were adversely impacted in the presence of vitamin D deficiency.

Murphy and co-authors say that these findings are novel and corroborate the animal and in vitro data suggesting a role for vitamin D in prostate cancer.

“Vitamin D supplementation may be a relevant strategy for preventing prostate cancer incidence and/or tumour progression in prostate cancer patients”, Murphy remarked in a press statement. “We will next evaluate genetic polymorphisms in the pathways of vitamin D metabolism to better understand the risk alleles underlying this association.”

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