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
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
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
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.
Roughly 20% of the men who took Avodart and 25% of the men who took a
placebo were diagnosed with prostate cancer during the study.
Taking Avodart was found to reduce the overall risk of a prostate cancer
diagnosis by 23%. The risk-reduction was 31% among men with elevated blood PSA
and a close family history of prostate cancer, Andriole tells WebMD.
GlaxoSmithKline, which manufacturers Avodart, paid for the study; Andriole
received consulting and lecture fees from GlaxoSmithKline and other drug
Andriole says Avodart may keep tumors from growing or it may shrink them to
the point where they are undetectable during a biopsy.