Men who regularly get moderate exercise may have a lower risk of developing prostate cancer - including aggressive, fast-growing tumors, a new study finds.

Researchers found that among 190 men who underwent biopsies for possible prostate cancer, those who exercised moderately - the equivalent of three to six hours of walking per week - were less likely to be diagnosed with the disease.

Compared with their sedentary counterparts, these men were two-thirds less likely to have a biopsy positive for prostate cancer. In addition, men who got the equivalent of one to three hours of walking each week had an 86 percent lower chance of having an aggressive form of the cancer.

he findings, which appear in the current issue of the Journal of Urology, do not prove that exercise helps prevent prostate cancer. But they could offer men yet more incentive to get active.

“If you need one more reason to exercise, this could be one,” said senior researcher Dr. Stephen J. Freedland, of the Duke University Prostate Center and the VA Medical Center in Durham, North Carolina.

[intv]

A number of studies have looked at the relationship between exercise and prostate cancer, and while most have pointed to a protective effect, about one-third have found no association, Freedland told Reuters Health.

One question has been whether the positive findings reflect a greater tendency of health-conscious exercisers to get screened for prostate cancer. This study avoided that issue, Freedland said, by focusing on men who were sent for biopsies after concerning findings from prostate specific antigen (PSA) testing or a digital rectal exam.

He and his colleagues found that among the 111 sedentary men in the study, half were diagnosed with cancer after biopsy. That compared with 27 percent of those men who got the equivalent of three to six hours of walking each week.

And among men diagnosed with prostate cancer, 51 percent of sedentary patients had more-aggressive cancer, versus 22 percent of those who had been mildly active - getting the equivalent of one to three hours of moderate walking per week.

Exercise itself remained linked to a lower risk of prostate cancer after the researchers accounted for a number of other factors, like age, weight and race.

Along with studies finding a relationship between exercise habits and lower prostate cancer risk, there is also research showing that the connection is biologically plausible, Freedland said.

For one, he noted, exercise has been shown to lower blood levels of testosterone and other hormones that may stimulate prostate tumor growth. Exercise is also believed to stimulate the immune system and the body’s natural antioxidant mechanisms, both of which may help prevent the development of prostate cancer.

SOURCE: Journal of Urology, November 2009.