25-Hydroxyvitamin D at time of breast cancer diagnosis and breast cancer survival.

ABSTRACT

PURPOSE: Previous studies have shown that low levels of 25-hydroxyvitamin D (25(OH)D) are associated with a poorer breast cancer survival. The relationship between vitamin D status and breast cancer outcomes is however still debated. The aim of the present study was to investigate the association between 25(OH)D blood levels measured at time of diagnosis and event-free survival (EFS) and overall survival (OS) in a large cohort of patients with early-stage primary invasive breast cancer. METHODS: From April 2008 to April 2013, 25(OH)D status was measured at time of diagnosis in all women operated for early stage primary invasive breast cancer at Rigshospitalet, Copenhagen, Denmark. Associations between 25(OH)D and EFS and OS were investigated using a Cox Proportional hazards model, adjusting for age, disease characteristics, time period, and BMI. Differences in survival were evaluated by hazard ratios (HR). RESULTS: In the present study, 2510 women with primary invasive breast cancer were included. Women with the lowest 25(OH)D levels (≤ 52 nmol/L) had an inferior EFS with a HR of 1.63 (95% CI 1.21-2.19) compared to women in the third quartile (76-99 nmol/L). Women with the highest 25(OH)D levels (≥ 99 nmol/L) also had an inferior EFS with a HR of 1.37 (95% CI 1.02-1.83). Plotting 25(OH)D status against EFS, the association was inversely J-shaped. For OS, a similar association with 25(OH)D status was observed. CONCLUSION: We confirmed previous findings suggesting that a low 25(OH)D status is associated with an inferior breast cancer survival, but unlike previous findings, we found an indication of poorer breast cancer survival also among women with high 25(OH)D levels.