Circulating vitamin D concentrations and breast cancer incidence among Black/African-American and non-Black Hispanic/Latina women

Abstract

BACKGROUND AND AIM: Vitamin D has anti-carcinogenic properties and may protect against breast cancer. Although Black/African American women and Hispanic/Latina women have lower circulating vitamin D levels than non-Hispanic white women, few studies have examined the association between vitamin D and breast cancer within these racial/ethnic groups. Using a case-cohort sample of Black/African American and non-Black Hispanic/Latina women from the US-based Sister Study cohort, we estimated the association between circulating 25-hydroxyvitamin D [25(OH)D] and incident breast cancer. METHODS: We compared concentrations of circulating 25(OH)D in blood samples collected at baseline from 405 women (281 Black/African American, 124 non-Black Hispanic/Latina) who developed breast cancer to concentrations in 1,511 women (1,061 Black/African American, 450 non-Black Hispanic/Latina) randomly selected from the cohort. Participants were aged 35-74 years and had a sister previously diagnosed with breast cancer but no breast cancer themselves at enrollment (2003-2009). Race/ethnicity was self-identified and 25(OH)D and 24,25(OH)2D, a biomarker of vitamin D catabolism, were assessed using liquid chromatography/tandem mass spectrometry. We used multivariable-adjusted Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS:Over a mean follow-up period of 9.2 years, women with blood 25(OH)D concentrations greater than the median level for the sub-cohort (22.6 ng/mL) had lower breast cancer rates than women with concentrations 22.6 ng/mL (HR=0.76, 95% CI: 0.59-0.97). The inverse association appeared stronger among non-Black Hispanic/Latina women (HR=0.55, 95% CI: 0.34-0.88) than among Black/African American women (HR=0.88, 95% CI: 0.66-1.17; p-for-heterogeneity=0.08). We did not see clear differences in the association by menopausal status, time since blood draw, or according to tumor characteristics. Neither 24,25(OH)2D nor the 24,25(OH)2D to 25(OH)D ratio were associated with breast cancer risk. CONCLUSIONS:This prospective study provides further evidence that vitamin D may be inversely associated with breast cancer incidence in non-Black Hispanic/Latina and Black/African American women. KEYWORDS: Cancer and cancer precursors, Biomarkers of exposure, Environmental epidemiology, Environmental disparities, Molecular epidemiology