Characterization of 25-OH vitamin D (Vit D) and factors associated with obesity in patients with high-risk breast cancer (BC): NCIC CTG MA.21.

1578 Background: Obesity (associated with poor BC outcomes) has been inversely associated with Vit D which, in turn, has been inconsistently associated with BC outcomes. We evaluated Vitamin D and its relationship to obesity related factors in a RCT of adjuvant chemotherapy in BC. Methods: 2,104 patients ≤ 60 years were enrolled onto NCIC CTG MA.21 and randomized to CEF, EC/T or AC/T. Serum was collected prerandomization from 934 patients. Vit D was assayed by radioimmunoassay (DIASORIN, Stillwater, MN). To examine Vit D associations we calculated Spearman correlation coefficients for age (years), estradiol, IGF-1, SHBG, insulin, leptin, glucose, BMI, HOMA (homeostasis model assessment, an estimate of insulin sensitivity) and we calculated ANOVA for season of blood draw, race, menopausal status, ECOG PS, nodal status, surgery, ER, grade. Multivariate Fisher linear step-wise forward discriminant analyses were performed to identify obesity-related factors associated with Vit D. Results: Means (SD) for age a...