Randomized Trial of the Effects of Vitamin D on Prostate Cancer-associated Lesions and on Vitamin D Metabolites in Prostate

Epidemiologic, laboratory, and clinical reports all suggest that vitamin D3 (cholecalciferol) plays a desirable role in the prevention and prognosis of prostate and other cancers. Prostate cancer cells possess both of the enzymes required to convert vitamin D to the active paracrine hormone, calcitriol. However, the dose-response relationship between serum levels of calcidiol (vitamin D status) and prostate tissue levels of calcidiol and calcitriol is yet to be defined. As a neoadjuvant, prior to radical prostatectomy (for 4-6 wk) vitamin D3 [400 IU (control group), 10,000 IU or 40,000 IU/day] will be given to 90 men randomized, double-blinded, 30 per dose. Immediately after surgery, the pathologist will obtain a few grams of prostate tissue, some of which will be used to assay calcidiol and calcitriol within prostate. From the embedded prostate, we will prepare immunohistochemically stained sections to characterize cellular responses and morphological changes. Our hypothesis is that vitamin D will increase intraprostate calcitriol concentration and thereby lower cellular proliferation (as judged by the markers MIB-1 and p27) in zones of Gleason pattern 3 prostate cancer and in pre-cancerous (PIN) lesions. We expect that our results will provide surrogate outcomes to justify larger trials of vitamin D for treatment of prostate cancer. This research has the potential to: 1. Provide direct evidence at the cellular level using clinical samples that vitamin D lowers cellular proliferation in prostate cancer, 2. Provide guidance about the serum calcidiol concentrations (and thereby vitamin D doses) that should be targeted for such studies, and 3. Eventually support other research directed at vitamin D as a primary prevention strategy.