I am pondering the announcement of a study to be discussed next weekend on Vitamin D and breast cancer. I'm starting to look through the ASCO (American Society of Clinical Oncology) abstracts on breast cancer looking for some exciting news - this study has received the most press already.
Dr. Pamela Goodwin's study looked at Vitamin D levels in 512 women diagnosed with breast cancer. Those women who had lower vitamin D levels had a lower distant disease free survival and overall survival (i.e. cure rate), at least among women whose breast cancers were estrogen receptor positive.
This creates worry - or perhaps hope. Could supplementing Vitamin D levels improve ones chance of cure? So far I have only the abstract to ponder. The answer would seem to be unclear. If your breast cancer is ER negative there does not appear to be this correlation from the study.
For women whose cancer is ER positive? I'm not yet sure. Dr Goodwin also showed that there was a relationship between low vitamin D levels and high tumor grade - so it will be necessary to understand a little more of the analysis. And association does not necessarily mean cause and effect - as Dr Goodwin was quoted as saying in an online interview. "At the moment it is premature to recommend vitamin D for women who are diagnosed with breast cancer".
Many epidemiologic studies in cancer have "biologic plausibility" meaning that there could be a biologic reason why one group might have a higher cure rate than another. But oftentimes, this does not pan out in the long run. A classic example of this was the Women's Health Initiative - we had several, very high quality epidemiologic studies that pointed to a benefit of hormone replacement therapy, yet when the randomized trial was finally performed it turned out that hormone replacement therapy seemed detrimental to women's health.
How would this change my management or my recommendations? Well, it would appear that 38% of women in this study were Vitamin D deficient - therefore it's certainly reasonable to measure a Vitamin D level in patients and replace Vitamin D for general health reasons, independent of the study findings.
When I obtain bone density for women who may be placed on aromatase inhibitors there have been many occasions where bone thinning is surreptitiously discovered.
Another study presented at the American Association of Cancer Research meeting showed that postmenopausal women with breast cancer who had a high intake of plant lignans were 70% less likely to die of their breast cancer.