From the Department of Medical Oncology, Princess Margaret Hospital (O.C.F. and P.J.G.), Mount Sinai Hospital (P.J.G.), and the Samuel Lunenfeld Research Institute (P.J.G.), Toronto, Canada
Authors disclosures of potential conflicts of interest are found at the end of this article.
Address reprint requests to Dr. Pamela J. Goodwin, Mount Sinai Hospital, 1284-600 University Avenue, Toronto, Ontario M5G 1X4, Canada; e-mail: pgoodwin{at}mtsinai.on.ca
Overview: The inverse association between solar radiation exposure and cancer mortality was identified over 60 years ago, and vitamin D was proposed to be responsible for this correlation almost 30 years ago. Literature regarding breast cancer risk and vitamin D has increased substantially over the past 10 years; however, definitive evidence regarding a causal relationship between vitamin D deficiency and breast cancer risk is still lacking. This article reviews the knowledge to date regarding vitamin D and breast cancer prognosis. In addition, an overview of the biology of vitamin D, as well as a review of sources of vitamin D, preclinical data regarding vitamin D and cancer, and normal ranges of vitamin D in the body will be presented. Finally, given current research controversy, practical clinical recommendations are suggested.