A new meta-analysis, published by the International Journal of Cancer Research and Treatment, demonstrates a strong association between increased vitamin D [25(OH)D] serum levels and improved survival for patients with breast cancer. The study, although not conclusive, strongly suggests that, rather than waiting for the results of further studies to come out, breast cancer patients can reap immediate benefits by having their health care providers keep close watch over their vitamin D levels and target for blood concentrations exceeding 30 nanograms per milliliter.
The investigators conducted a PubMed search of observational studies, performed between 1966 and 2010, that looked at 25(OH)D serum levels and breast cancer risk. Out of 77 studies identified as potential candidates, five met inclusion criteria. These studies took place between 2009 and 2013. The number of breast cancer patients in the study totaled 4443, and these were divided into five groups based on a scale of 25(OH)D serum levels, ranging, from 17 ng/ml or below, to 30 ng/ml or greater.
The results of the analysis showed a 44 percent lower risk of death between women with higher versus lower serum levels of vitamin D. These higher levels fell in the range of 30 to 80 ng/ml. Noteworthy is the fact that average vitamin D serum levels for US breast cancer patients is a mere 17 ng/ml, a far cry from those levels suggestive of an increased chance of survival.
Vitamin D is perhaps best known for its role in bone health, as it helps regulate calcium in the body. But it is also capable of many other functions, not yet fully understood. So how does vitamin D increase survival rates for breast cancer patients?
One of the investigators, Cedric Garland, DrPH, of the University of California, San Diego, has researched vitamin D’s role in cancer prevention quite extensively and offers a possible explanation. As a basis for a theory of Vitamin D cancer prevention, Garland identifies several stages of tumor growth but highlights three as the most critical; differentiation, apoptosis, and angiogenesis. Differentiation refers to the process whereby an embryonic cell matures into a a certain cell type. Cancer cells have a tendency to proliferate while not yet having undergone differentiation. Apoptosis refers to programmed cell death, a natural process that may be defective in cancer cells. Finally, angiogenesis is a process by which new blood vessels arise from existing ones. Tumor cells emit chemical signals that trigger this process. Without a blood supply, tumors die and , therefore angiogenesis has been a major focal point in cancer research.
Garland proposes that vitamin D prevents tumor growth by up-regulating proteins that inhibit rapid cell division. He also suggests that there may be an association between serum 25(OH)D and breast cancer survival that “depends on maintaining differentiation, promoting, apoptosis, and inhibiting angiogenesis”.
The investigators point out that the results of the study do not preclude the possibility of reverse causality, that perhaps severe breast cancer depletes 25(OH)D levels, but they also note that no laboratory study, to date, has shown tumors to be capable of such. In the meantime, there is evidence that sufficient levels of vitamin D may increase the chances of survival for breast cancer patients.
By Robert Wisnewski