Canadian and international researchers are recruiting men for a clinical trial to test whether combining a high-dose vitamin D pill with chemotherapy improves treatment for advanced prostate cancer.

Dr. Kim Chi of the B.C. Cancer Agency and two other lead investigators will study about 1,000 men over the next two years.

Currently, there is little to offer prostate cancer patients who have stopped responding to standard hormone therapy, Chi said.

The clinical trial will test a high-dose pill of calcitriol, a biologically active form of vitamin D and a naturally occurring hormone, together with the chemotherapy drug docetaxel.

Researchers will compare survival rates among patients with advanced prostate cancer.

The treatment is designed to reduce the toxic side-effects linked to high-dose supplements.

It's estimated that 20,700 men in this country will be diagnosed with prostate cancer this year and 4,200 will die from the disease, according to the Canadian Cancer Society.

With files from the Canadian Press