Men with very early-stage prostate cancer can have their outcomes influenced by diet and exercise. This was a very small study:

A small study of men with early stage prostate cancer, who were in a watchful-waiting phase, suggests that intensive changes in diet and lifestyle could stop or even reverse biochemical progression of the disease.

That's according to Dean Ornish, M.D., the crusader for ultra-low-fat diets, and colleagues, who published their findings in the September issue of the Journal of Urology.

Among 93 men with early stage prostate cancer who opted for watchful waiting, those in the group who were randomly selected to make radical lifestyle changes had a 4% decrease in prostate-specific antigen levels at one year. In contrast, men who made no lifestyle changes had a 6% rise in PSA over the same period.

(Osterweil, "Spartan Diet and Lifestyle May Prevent Prostate Cancer Growth", MedPage Today, Aug.11)