In Reply Braillon and Mormile raised some interesting points regarding our report of a positive association of serum vitamin D level with better breast cancer prognosis in the Pathways Study.1
Kaplan-Meier survival curves by tertiles of vitamin D level only began to separate after day 1500, similar to findings in an earlier study showing separation after 4 years.2 In addition to analyzing vitamin D levels in tertiles, we also tested it as a continuous variable, which showed similar trend (overall survival per 10 ng/mL increment: adjusted hazard ratio [HR], 0.81; 95% CI, 0.70-0.94; P = .005).
Yao S, Ambrosone CB, Kushi LH. Vitamin D and Breast Cancer Survival—In Reply. JAMA Oncol. Published online June 08, 2017. doi:10.1001/jamaoncol.2017.1477