Improved Clinical Outcomes Associated With Vitamin D Supplementation During Adjuvant Chemotherapy in Patients With HER2+ Nonmetastatic Breast Cancer

Vitamin D (VD) supplementation has pleiotropic effects that extend beyond their impact on bone health, including the disruption of human epidermal growth factor receptor 2 (HER2) signaling through the ErbB2/AKT/ ERK pathway. We performed a retrospective review of patients who received VD supplementation during neoadjuvant chemotherapy (n [ 134) and those who did not (n [ 112). In our final multivariate model, VD use was associated with improved disease-free survival (DFS) (hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.15-0.88); P [ .026). To the best of our knowledge, our study is the first to report a significant improvement in DFS for patients who received VD supplementation concurrently with trastuzumab-based chemotherapy for HER2-positive (HER2 D ) nonmetastatic breast cancer. Background: Vitamin D (VD) supplementation has pleiotropic effects that extend beyond their impact on bone health, including the disruption of downstream VD receptor signaling and human epidermal growth factor receptor 2 (HER2) signaling through the ErbB2/AKT/ERK pathway. In the present study, we examined our institutional experience with patients having nonmetastatic HER2-positive (HER þ ) breast cancer and hypothesized that those patients who received VD supplementation during neoadjuvant chemotherapy would have improved long-term outcomes. Patients and Methods: We performed a retrospective review of all patients (n ¼ 308) given trastuzumab-based chemotherapy between 2006 and 2012 at the University of Miami/Sylvester Comprehensive Cancer Center (UM/SCCC). We identified 2 groups of patients for comparison—those who received VD supplementation during neoadjuvant chemotherapy (n ¼ 134) and those who did not (n ¼ 112). Univariate and multivariate Cox proportional hazard regression models were fitted to overall survival (OS) and disease-free survival (DFS). Results: More than half of the patients received VD during neoadjuvant chemotherapy (54.5%), with 60% receiving a dose < 10,000 units/wk and 33.3% having aV D deficiency at the start of therapy. In our final multivariate model, VD use was associated with improved DFS (hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.15-0.88; P ¼ .026], whereas larger tumor size was associated with worse DFS (HR, 3.52; 95% CI, 1.06-11.66; P ¼ .04). There were no differences in OS based on any of