Abstract P3-08-08: Vitamin D status at breast cancer diagnosis: correlation with patient and tumor characteristics

Abstract

Abstract Background: Despite many preclinical studies showing anti-neoplastic activities of vitamin D on breast cancer, findings from epidemiologic studies and randomized trials on the relationship between vitamin D and breast cancer remains inconclusive. It is possible that tumor heterogeneity in breast cancer may mask these associations. Variations in vitamin D metabolism might explain some racial disparities in breast cancer. We aimed to examine the association of serum vitamin D levels with patient and tumor characteristics. Methods: We conducted an IRB approved retrospective chart review, identifying all breast cancer patients with documented pretreatment serum level of 25-hydroxyvitamin D (25(OH)D) between February 2011-May 2012. The following clinical data were collected for each patient: age at diagnosis, ethnicity, menopausal status, largest 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), HER2+, triple negative (TN) (ER, PR, and HER2 negative). Vitamin D deficiency, insufficiency, and sufficiency were defined as 25(OH)D <20 ng/mL, 20–29 ng/mL, and ≥30 ng/mL, respectively. Descriptive variables were analyzed using one-way Anova test. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated from logistic regression models. Results: Among 86 breast cancer patients identified, median age was 60 years (range 27–88). Ethnicities of the patients: 47 (55%) Caucasian, 18 (21%) African American, 15 (17%) Hispanic, and 6 (7%) Asian. Twenty eight (33%) were premenopausal, and 58 (67%) were postmenopausal. African Americans had the lowest mean 25(OH)D levels among different ethnicities (p = 0.0042). Patients with tumors >2 cm had lower mean vitamin D levels compared to those with tumors ≤ 2 cm (p = 0.037). 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 < 0.001), with large tumor size (p < 0.001), and with tumors that were ER negative (p = 0.003). There was also a trend toward lower mean vitamin D levels in those with TN breast cancer compared to other molecular subtypes. In subgroup analysis, being African American and having TN breast cancer significantly correlates with having vitamin D deficiency (p = 0.0001). Conclusion: In premenopausal women, lower vitamin D levels were associated with African American race, larger tumor size, and ER negativity. African Americans with TN breast cancer were more likely to be vitamin D deficient. This might support the hypothesis 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 2012;72(24 Suppl):Abstract nr P3-08-08.