A medication commonly prescribed to treat enlarged prostates may have an even more important use: slowing the growth of early stage prostate cancer.

In a study published Monday in the journal The Lancet, Canadian researchers have found that dutasteride (often sold as Avodart) may eliminate the need for aggressive treatment in men with low-risk prostate cancer.

That's good news for those men whose cancer is growing so slowly, it's not expected to shorten their lives. These men are often told to take a "watch and wait" approach. But many have said they don't feel comfortable doing nothing about their cancer.

Now, Canadian researchers say dutasteride can help make watchful waiting more bearable.

The study followed 300 men, aged 48 to 82 years old, with low risk prostate cancer that was being actively watched by their doctors. Half the men were given a daily placebo, while the other half took 0.5 mg of dutasteride a day for three years.

The men then underwent biopsies at 18 months and three years later to measure their disease progression. The researchers found:

• 48 per cent given the placebo experienced disease progression
• 38 per cent of the men receiving dutasteride experienced disease progression

Additionally, men treated with dutasteride were more likely to have no cancer detected in their final biopsy. In 50 of the men on the dutasteride group, doctors could find no cancer, compared to 31 men in the placebo group.

It's not clear whether the drug helped to save any lives, since there were no prostate cancer-related deaths during the study, nor were there any instances of disease spread.

But the men taking the medication did report less anxiety in questionnaires throughout the study, compared with those given placebo.

The study's lead investigator, Dr. Neil Fleshner of Princess Margaret Hospital in Toronto, says the drug could allow more men to avoid surgery, which carries the risk of side effects such as impotence and incontinence.

"This drug may not save a life, but it will prevent men whose cancer will pose no long-term risk, stave off surgery or radiation or treatment with side effects," he told CTV News.

There were more drug-related side effects in the men in the dutasteride group compared to those given placebo. Those side effects included adverse sexual events or breast enlargement or tenderness.

And the authors note that they have no reason to believe the drug can help slow the progression of high-grade prostate cancer.

The study was sponsored by Avodart's maker, GlaxoSmithKline. Fleschner reports the company will not be seeking a formal approval for use of the drug in low-grade prostate cancer management.

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip