A new study has reported that women with low blood levels of vitamin D tend to be diagnosed with more aggressive breast cancer than women with adequate vitamin D levels. The study was designed to investigate the associations between circulating vitamin D, demographic factors, and prognostic pathological and genetic characteristics of breast cancer. Population studies have reported that women with low circulating vitamin D levels (as measured by 25-hydroxyvitamin D (25-OH)) have increased risk of breast cancer and related mortality. However, little research has been performed to examine vitamin D levels as they relate to prognostic variables in breast cancer patients.

The study included 155 women who had breast cancer surgery at the University of Rochester between January 2009 and September 2010. Data concerning vitamin D levels were obtained for the one-year period before and after surgery (74% of the vitamin D measurements were taken within six months of surgery). Data was also collected regarding prognostic variables such as age, race, menopausal status, Oncotype DX score (an estimate of likelihood of recurrence), TNM (tumor-node-metastasis) stage, hormone receptor (ER/PR) status, and HER2 expression.

Premenopausal women with breast cancer were more than three times as likely to have suboptimal vitamin D levels as postmenopausal patients. Non-Caucasian patients were also over three times as likely to have suboptimal vitamin D levels as the Caucasian women in the study. Study participants with invasive breast cancer were more than twice as likely to have suboptimal vitamin D levels as women with noninvasive breast cancer such as DCIS. Invasive breast cancer patients also had lower average 25-OH vitamin D levels than women with noninvasive breast cancer (average for invasive breast cancer patients was 30.5 ng/mL compared to 36.9 ng/mL for those with in situ disease). A significant correlation was found between decreasing vitamin D levels and increasing Oncotype score. Breast cancer patients who had estrogen receptor negative (ER-) and triple negative (ER-/PR-/HER2-) tumors were also more than twice as likely to have suboptimal levels of 25-OH vitamin D. The authors conclude that breast cancer patients with suboptimal vitamin D levels were more likely to have tumors with more aggressive characteristics, worse prognostic markers (ER- and triple-negative tumors), and higher recurrence risk (Oncotype scores), lending support to previous findings that survival among vitamin D deficient breast cancer patients may be decreased. Further research is needed to elucidate the biological relationship between vitamin D and prognostic breast tumor markers.

Please see our article on vitamin D and breast cancer for more information on how vitamin D influences breast cancer risk and survival.