Exercise may reduce Caucasian men's risk of developing prostate cancer, according to a new study published on-line Monday in CANCER, a peer-reviewed journal of the American Cancer Society.

Lionel Banez, of the Durham Veterans Affairs Medical Center, and colleagues asked 307 men (164 white; 143 black) undergoing a prostate biopsy to complete a survey that assessed their exercise amounts per week. The exercise categories included sedentary, mildly active, moderately active, and highly active.

Among Caucasians, men who were moderately or highly active were 53 percent less likely to have biopsy results indicating that they had prostate cancer compared with men who were sedentary or mildly active. There was no association between exercise amount and prostate cancer among black men.

The investigators also looked to see if exercise influenced the grade of tumors that were detected in men who did develop prostate cancer. Among men with cancer, those who exercised had a 13 percent reduced risk of having high grade disease, meaning that their cancer cells looked particularly abnormal under a microscope and were likely to quickly grow and spread. When this relationship was further explored as a function of race, it remained significant in Caucasians but not in African Americans.

"Further studies are needed to investigate the mechanism behind this racial disparity in deriving cancer-related benefits from exercise which disfavors African-American men," said Banez in a statement.