Vitamin D may hold promise for prostate cancer, studies show

A new high-dose calcitriol pill designed as a cancer therapy, given in combination with docetaxel (Taxotere), appears to extend the lives of men with advanced prostate cancer, according to a recent study. The toxicity of the combination therapy proved to be no greater than for research subjects who received docetaxel alone.

"While we've known about the anti-tumor potential of vitamin D, toxicity has been a significant issue to be overcome in making it a successful part of prostate cancer therapy," said co-author Tomasz Beer, MD, of Oregon Health & Science University Cancer Institute, Portland.

The randomized, double-blinded, placebo-controlled trial included 250 subjects at 48 sites between September 2002 and January 2004. The team estimates that subjects receiving combination therapy with the calcitriol formulation, known as DN-101, plus docetaxel survive 7.1 months longer than those who received docetaxel alone.

Overall PSA responses occurred more frequently in subjects receiving the combination (63%) versus docetaxel alone (52%). While the difference between the two arms did not reach statistical significance, the combination results represent a historically strong PSA response. Six months into the study, 58% of DN-101 and 49% of placebo-treated patients had experienced a PSA response, the researchers reported at the American Society of Clinical Oncology annual meeting in Orlando, FL.

A separate study discussing the effects of vitamin D has found that increased exposure to sunlight may decrease the risk of prostate cancer. Three cancer centers found that the prostate cancer risk for men with high sun exposure was half that of men with low sun exposure.

In men with certain gene variants, risk was reduced even further, by as much as 65%, the researchers said.

"We believe that sunlight helps to reduce the risk of prostate cancer because the body manufactures the active form of vitamin D from exposure to sunlight," said lead author Esther John, PhD, of the Northern California Cancer Center, Fremont.

The findings appear in Cancer Research (2005; 65:5470-9).