Prognostic associations of 25 hydroxy vitamin D in NCIC CTG MA.21, a phase III adjuvant randomized clinical trial of three chemotherapy regimens in high-risk breast cancer.

Low vitamin D levels have been associated with poor breast cancer outcomes in observational studies. We examined the association of vitamin D blood levels with relapse-free survival (RFS), breast cancer-specific survival (BCSS), and overall survival (OS) in the MA.21 randomized clinical trial.