Abstract P3-01-03: Vitamin D levels at breast cancer diagnosis: Association with patient and tumor characteristics

Background: Despite many preclinical studies showing the anti-neoplastic effects of vitamin D on breast cancer, findings from epidemiologic studies and randomized trials remain inconclusive. It is possible that tumor heterogeneity in breast cancer may mask these associations. Variations in vitamin D metabolism may explain some racial disparities in breast cancer. We aimed to examine the association of serum vitamin D levels with individual patient and tumor characteristics. Methods: We conducted an IRB approved retrospective chart review, identifying all breast cancer patients with documented pretreatment serum levels of 25-hydroxyvitamin D (25(OH)D) between February 2011-May 2013. The following clinical data were collected for each patient: age at diagnosis, ethnicity, menopausal status, tumor size (mm), lymph node status, estrogen receptor (ER), progesterone receptor (PR), and HER2 status. Based on ER, PR, and HER2, patients were categorized into three molecular subtypes: 1) Hormone receptor (HR)+ (ER or PR positive, HER2 negative), 2) HER2+, and 3) triple negative (TN; ER, PR, and HER2 negative). Descriptive variables were analyzed using a one-way Anova test. Results: Among the 200 breast cancer patients identified, the mean age was 55.9 years (range 29-90). Ethnicities of the patients were as follows: 104 (52%) Caucasian, 43 (22%) African American, 29 (15%) Hispanic, and 16 (8%) Asian. Seventy six patients (38%) were premenopausal, and 124 (62%) were postmenopausal. African Americans were found to have higher rates of triple negative tumors compared to all other ethnicities (24.4% vs. 11.6%, p = 0.029). Younger women had lower mean serum 25(OH)D levels compared to older women (p = 0.033). Lower mean 25(OH)D levels were seen in ER negative tumors compared to ER positive tumors (p = 0.0102). Mean 25(OH)D levels were lower in African American, Hispanic, and Asian breast cancer patients when compared to Caucasians (p = 0.0004). When stratifying by menopausal status, serum 25(OH)D levels differed more by tumor characteristics among premenopausal women than postmenopausal women. In premenopausal women, lower vitamin D levels were seen in patients who were African Americans (p = 0.0185), and with tumors that were ER negative (p = 0.0083). There was also a trend toward lower mean vitamin D levels in those with TN breast cancer compared to other molecular subtypes. Conclusion: In premenopausal women, lower vitamin D levels were associated with African American race, younger age, and ER negative tumors. This may suggest that African Americans have defective vitamin D metabolism that may contribute to a more aggressive breast cancer phenotype. Further studies are warranted. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-01-03.