Vitamin D Deficiency and Breast Cancer Outcome
Low Vitamin Linked to Worse Outcome in Breast Tumor
Mar 3, 2009
On 31 May 2008, at the American Society of Clinical Oncology (ASCO) 2008 Annual Meeting, Dr Goodwin from the University of Toronto and Mount Sinai Hospital, in Ontario and co-workers presented their Canadian study on the association between vitamin D deficiency and bad outcome in breast cancer in 512 women. The study showed that Women who had very low levels of vitamin D when they were diagnosed with breast cancer were more likely to have aggressive disease. They were 94% more likely to develop metastases and 73% more likely to die than women with normal levels of vitamin D at diagnosis.
Even though an association between vitamin D deficiency and bad breast cancer outcome was evident, the causal effect could not be established at the moment. Dr Goodwin explained that their results would need to be replicated in other clinical studies, preferably then followed by a randomized clinical trial to examine the effect of raising vitamin D levels on outcomes in breast cancer. Before such studies have been completed, clinicians and researchers are reluctant to recommend or prescribe vitamin D supplement to women diagnosed with breast cancer. At this stage, it is still uncertain and unproven that correcting a vitamin D deficiency will improve the outcomes of treatment on these women.
Many Women were Found to be Deficient in Vitamin D
The study also revealed the surprising finding of a high proportion of asymptomatic patients with vitamin D deficiency. The researchers were surprised that so many women had low levels of vitamin D. 37.5% women were "deficient" and had vitamin D levels below 50 nmol/L. Another 38% of patients were classified as "insufficient". Only 24% of women had categorically "sufficient" vitamin D levels (more than 72 nmol/L). Researchers compared the outcomes of these 3 groups of women at a median follow-up of 11.6 years; there were significant differences in both distant disease-free survival and overall survival between the groups with sufficient and deficient levels of vitamin D at diagnosis. In their study, most of the deaths were a direct result of breast cancer. Paradoxically, the investigators found out that when there could be an increased risk for death if vitamin D levels would rise to the levels over >120 nmol/L. Their conclusion was for all women to have their vitamin D levels checked (and vitamin D supplements should be given to the women with the deficiency to optimize their long term cancer outcome).
Why? Vitamin D Might Retard the Growth of Breast Cancer
Dr Goodman explained that breast cancer cells had vitamin D receptors in their nuclei, and activation of these receptors could actually change the molecular machinery. Hence vitamin D circulating in the blood might actually slow the growth and progression of breast cancer.
Source of information
American Society of Clinical Oncology 2008 Annual Meeting: Abstract 511.
