Breast cancer in Marin linked to vitamin D receptor differences

Breast cancer risk has been shown in numerous studies to be modified by vitamin D status. Vitamin D acts by communicating with its receptors on several membranes. These receptors occur in different genetic types or 'versions' (polymorphisms). The high incidence of breast cancer in Marin County, California has stumped investigators for years. Now a study just published in the Journal of the American College of Surgeons correlates breast cancer incidence in Marin with vitamin D receptor polymorphisms. The authors state:

"Marin County, California has very high incidence of breast cancer. Traditional risk factors, such as those included in the Gail model, do not effectively stratify breast cancer in this population. This retrospective case-control pilot study evaluates DNA from volunteers from a previous Marin County breast cancer epidemiology study. A polyfactorial risk model (OncoVue; InterGenetics Incorporated) that incorporates 22 polymorphisms in 19 genes and 5 clinical risk factors was used to stratify risk in Marin County women."

They performed DNA genotyping for vitamin D receptors on 164 women in Marin County who had been diagnosed with primary breast cancer and compared along with 174 matched controls. The lifetime risks for breast cancer of their subjects were determined and those at increased risk had their genotypes compared with the population at large. Their data revealed another aspect of the importance of vitamin D for breast cancer:

"The vitamin D receptor VDR ApaI A2/A2 (rs7975232) homozygous polymorphism was present in high frequency in elevated-risk women. Sixty-four percent of elevated-risk women had the VDR Apa1 A2/A2 genotype compared with only 34% in the overall study, a statistically significant 1.9-fold difference (p = 0.0003). VDR Apa1 A2/a1 and a1/a1 genotypes were also present, but in lower frequencies."

Differences in the vitamin D receptor (VDR) result in differences in vitamin D effectiveness and efficiency. (I encourage clinicians to see lectures from this year's Autoimmunity Congress recently posted here for the importance of VDR function in autoimmune disorders and CFS.)  This insightful study shows that there is an almost twofold increase in breast cancer risk with a particular genetic type of vitamin D receptor. The authors conclude:

"The high frequency of the VDR Apa1 A2/A2 homozygous polymorphism in women designated as elevated risk for breast cancer by the polyfactorial risk model might be related to the high incidence rates of breast cancer in Marin County, California. Vitamin D supplementation could modify risk of breast cancer in this population."

Important: Breast cancer causation is multifactorial; aspects of vitamin D function and VDR type and status are one aspect. Like everything else, recommendations for vitamin D must be made on an individual basis by practitioners who know how to evaluate vitamin D levels along with receptor status and response. I encourage women in Marin County and everywhere else to make sure this is part of their breast cancer prevention or treatment plan. Men: vitamin D receptor status may very well apply to prostate cancer too.