Serum 25-hydroxyvitamin D deficiency and increased risk of breast cancer among Korean women: a case-control study.

Despite the emerging literature supporting the beneficial role of vitamin D on various health outcomes including carcinogenesis, current evidence on the association between vitamin D and breast cancer is still largely inconsistent. Furthermore, this relationship is particularly under explored among Asian population. We conducted a large case-control study with Korean women. We obtained and compared serum 25-hydroxyvitamin D (25(OH)D) between breast cancer patients (N = 3634) and general population (N = 17,133). Moreover, we further examined the association between serum 25(OH)D and breast cancer risk stratified by menopausal status and hormone receptor (HR) status of the tumor. Adjusted odds ratio (OR) for breast cancer comparing women with deficient level of serum 25(OH)D to women with sufficient level of serum 25(OH)D was 1.27 [95 % confidence interval (CI) 1.15-1.39]. This association did not significantly vary by menopausal status [pre-menopause: 1.26 (95 % CI 1.09-1.45) vs. post-menopause: 1.25 (95 % CI 1.10-1.41)]. When stratified by HR status, the inverse association remained significant in both positive and negative statuses. However, this association was more pronounced in HR-negative breast cancer, particularly with triple-negative breast cancer patients (1.45, 95 % CI 1.15-1.82). Given the growing burden of breast cancer in Asia and dearth of studies examining the association between vitamin D and breast cancer risk in Asian women thus far, this study provides a meaningful evidence for potential preventive effect of vitamin D on breast cancer for this particular population.