Brisk walking might be able to help men who have been diagnosed with early-stage prostate cancer to cut their risk that the disease will progress, a new study has found.

The finding suggests that there is something that men who have prostate cancer can do to improve their prognosis, rather than just wait to see if the disease worsens.

Researchers at the University of California, San Francisco and the Harvard School of Public Health followed 1,455 men who had been diagnosed with early-stage prostate cancer. All the men had cancer that had not spread beyond the prostate.

The men reported their physical activity by questionnaire about 27 months after their original diagnosis.

Among the group, there were 117 "events," including an elevation of prostate-specific antigen (PSA) blood levels, which is an indication of cancer progression; the need for secondary treatments; spread of the cancer to the bone; or death directly related to the prostate cancer.

The researchers found that the men who walked at a pace of at least five kilometres per hour for three hours or more per week were 57 per cent less likely to die or to develop markers of cancer recurrence or the need for a second round of treatment for their disease.

The researchers found that exercise was beneficial in staving off progression regardless of the participants' age at diagnosis, the clinical features of their disease, or the type of treatment they received.

"The important point was the intensity of the activity – the walking had to be brisk for men to experience a benefit," Erin Richman, a postdoctoral fellow at UCSF, one of the authors of the study, said in a news release.

"Walking at an easy pace did not seem to have any benefit."

An earlier study, published earlier this year by UCSF's June Chan, and collaborators at the Harvard School of Public Health, showed that physical activity after diagnosis can reduce the risk of death in certain men with prostate cancer.

The new study complements this finding, and is the first to focus on the effect of physical activity after diagnosis.

"Our results provide men with prostate cancer something they can do to improve their prognosis," said Richman.

The study is published in the June 1 edition of Cancer Research.