Low Serum Vitamin D Associated With Increased Tumor Size and Higher Grade in Premenopausal Canadian Women With Breast Cancer.

Introduction: This study investigated the association of Vitamin D with tumor characteristics in pre and postmenopausal women.

Patients And Methods: A prospective cohort of 476 women with incident stage I-III breast cancer (BC) in Alberta, Canada comprised the study population. Vitamin D was measured as 25(OH)D concentration in serum samples collected at diagnosis (presurgery and prior to treatment initiation).