The effects of vitamin D levels on risk and prognosis of ovarian cancer: a systematic review
Ovarian cancer is the eighth most common cancer in women with the highest mortality rate of all gynecological cancers. Serum vitamin D level has been explored as a possible modifiable risk factor for development and progression of this disease. The proposed study aims to answer the questions: do women with low levels of vitamin D have a higher risk for developing ovarian cancer and, do low vitamin D levels at the time of ovarian cancer diagnosis predict a poorer prognosis? A systematic search was performed in PubMed, CINAHL, Cochrane, and Scopus. Cohort, case-control, in vivo, in vitro, and ex vivo studies assessing the effect of vitamin D levels on the risk of developing ovarian cancer, prognosis at time of diagnosis of ovarian cancer, or both, published in English since July of 2008 were included. Eighteen studies were included in this review. Six of the nine case-control studies found ovarian cancer patients to have lower vitamin D levels. Of the studies to investigate survival rates, both articles reported significant increases in survival rate in vitamin D sufficient patients. Cohort studies found similar mixed results to the case-control experiments, while experimental studies produced significant results pertaining to vitamin D's ability to reduce proliferation and decrease progression in ovarian cancer cell lines. However, two large-scale, nested studies noted no significant association between low vitamin D levels and ovarian cancer incidence. This review has determined that lower vitamin D levels are a risk factor for the development of ovarian cancer. In addition, it was found that ovarian cancer patients with low vitamin D levels have a worse prognosis comparatively.