Men diagnosed with low-risk, localized prostate cancer who were given the drug dutasteride had a significant delay in progression of the disease over a three-year period, according to a study published online Monday in The Lancet, a respected medical journal.

It’s “good news” for men who have low-risk prostate cancer because aggressive treatment, such as surgery and radiation, “can have a major impact on their quality of life, with risks of impotence and incontinence,” said Dr. Neil Fleshner, head of the urology division at Toronto’s University Health Nework (UHN), who led the study.

The three-year clinical trial involved 302 men between the ages of 48 and 82, who had low-risk, localized prostate cancer and were being regularly monitored for clinical changes in their condition, a treatment option called “active surveillance.”

It was funded by GlaxoSmithKline, which manufactures Avodart, a brand-name version of dutasteride.

Half of the study participants received a placebo and all of the men underwent biopsies at 18 months and three years.

The study showed that 48 per cent of those who received the placebo had a progression in the disease, compared to 38 per cent of those who got the drug.

The final biopsies at the end of the study indicated that the men who got the drug were less likely to have cancer detected — 36 per cent, compared to 23 per cent. That doesn’t mean the cancer is cured but it’s “shrunk so small we can’t find it,” said Fleshner.

Dutasteride, commonly used to treat enlarged prostate, works “by inhibiting the male sex hormone that causes the enlargement in the first place,” said Fleshner. (There’s no link between enlarged prostate and prostate cancer.)

In a critical comment, also published Monday by The Lancet, British doctor Chris Parker said “the study duration of just three years was very short compared with the natural history of prostate cancer. Long-term outcomes remain unknown.”

A small percentage of the men in the study who were on the drug reported side effects, including difficulty with erections or desire (5 per cent), breast tenderness or enlargement (3 per cent.)

Prostate Cancer Canada estimates that 25,000 new cases of prostate cancer will be diagnosed this year and 4,100 men will die from the disease. About one-third of prostate cancer cases are considered aggressive and fast-growing.