March 31, 2010 -- A widely prescribed drug used to shrink enlarged prostates appears to reduce the incidence of prostate cancer in men with an increased risk for the disease.
In a trial involving more than 8,000 men from 42 countries, those who took the drug Avodart had a 23% lower risk of being diagnosed with prostate cancer over four years of treatment, compared to men who did not take the drug.
The risk reduction was similar to that seen in an earlier large trial of Proscar, another drug in the chemical class known as 5-alpha-reductase inhibitors.
The drugs work by blocking the conversion of testosterone into a key hormone associated with prostate growth.
While the studies suggest a role for Avodart and Proscar in the prevention of prostate cancer, experts tell WebMD that important questions remain about using the drugs for this purpose.
"We now have two studies showing that two different drugs in this category can reduce the overall risk of prostate cancer," American Cancer Society Director of Prostate and Colorectal Cancers Durado Brooks, MD, tells WebMD. "But we don't have studies saying that they decrease the risk of death from prostate cancer."
A total of 8,231 men between the ages of 50 and 75 took part in the study, published in the New England Journal of Medicine.
All of the men had elevated blood levels of prostate specific antigen (PSA), which indicated an increased risk for prostate cancer. But none had evidence of cancer when biopsies were performed within six months of entering the trial.
Study researcher Gerald L. Andriole, MD, says a significant proportion of men screened for prostate cancer fall into this clinically ambiguous category of having elevated PSAs and negative biopsies.
"We know from experience that many of these men are likely to have microscopic prostate tumors that were missed by their original biopsy," he says in a news release.
The men were assigned to receive either placebo treatments or daily 0.5-milligram doses of Avodart for four years. Scheduled biopsies were performed two and four years after they entered the trial.