The average age was 50 and the average vitamin D levels was 58.1 nmol/L. Vitamin D levels were deficient (<50 nmol/L) in 192 women, insufficient (50 to 72 nmol/L) in 197 women and sufficient (> 72 nmol/L in 123 women. The average follow-up was 11.6 years with 116 women having distant recurrences and 106 women who died. Vitamin D levels were significantly lower in women with high grade tumors. Those women with vitamin D deficiency had an increased risk of distant recurrence and of dying, compared with those women who had sufficient serum vitamin D levels.
Commentary: This study is one more reason to test vitamin D levels- I would recommend it for all current or past breast cancer patients. In terms of using vitamin D levels to determine the initial risk for breast cancer, the evidence has been mixed, with some showing an association between latitude and risk of breast cancer, some showing an inverse relationship between vitamin D intake and breast density (a strong risk factor for breast cancer), but other studies showing vitamin D intake or blood levels of vitamin D inconsistently related to risk/incidence.
There have been some other attempts to use vitamin D levels as a prognostic indicator for breast cancer and mortality. Low vitamin D levels have been associated with increased breast cancer mortality and have also been shown to be significantly lower in women with locally advanced or metastatic disease compared with those women who have early breast cancers. Taking a vitamin D supplement to increase blood levels of vitamin D is one of the least expensive, safe strategies to reduce the risk of recurrence of breast cancer, as stated in this current study. For the rest of us… the research is full of good news about vitamin D and our health with studies demonstrating that higher blood levels of vitamin D is associated with lower rates of heart disease, ovarian cancer, multiple sclerosis, osteoarthritis and rheumatoid arthritis, bacterial vaginosis, and as mentioned, breast cancer.
It should be noted that the current studies, and in fact many studies, report vitamin D levels in the units of nmol/L. Other studies report ng/ml. This is a very important difference. It is important to compare one’s lab unit results for vitamin D levels with the proper target number and unit used. For reference, 75 nmol/L is equal to 30 ng/mL. In the current study, those women who had a vitamin D deficiency and reported as < 50 nmol/L would be equivalent to < 20 ng/ml.
Goodwin P, Ennis M, Pritchard K, et al. Prognostic effects of 25hydroxyvitamin D levels in early breast cancer. J Clinical Oncology 2009;27(23): 3757-3763