The drug, called Avodart, could also reduce the need for aggressive treatment in some men.
Prostate cancer can grow and spread slowly. That is why some men are urged to engage in so called watchful waiting when the cancer is first diagnosed.
But some patients feel uncomfortable doing nothing in the face of a cancer diagnosis. Scientists say Avodart could help these men feel comfortable with surveillance as opposed to radical treatment.
The findings are published in the journal The Lancet.
