The claim was made in a presentation Monday by Dr. Dean Ornish, founder and director of the Preventive Medicine Research Institute in Sausalito, Calif., at the annual meeting of the American Urological Association in Chicago.
Ornish has been preaching lifestyle change as a way to reverse heart disease for years, in medical journals and five best-selling books.
His prescription calls for a low-fat vegan diet supplemented with soy and oxidants, moderate aerobic exercise, stress management and psychosocial group support. Now he says the same regimen lowered levels of prostate-specific antigen (PSA), a marker of the cancer, in a one-year study.
The study included 87 men with diagnosed prostate cancer at an early stage, when doctors often choose to do nothing while they check on the progress of the tumor -- "watchful waiting," in medical terms. In the study, 41 of the men were assigned to observe the Ornish regimen carefully, under supervision. The others were allowed to follow the regimen if they chose, with no supervision.
At the end of three months, PSA levels dropped by 5 percent in the group following the regimen but rose by 1 percent in the control group, Ornish says. The difference in PSA levels was greater after one year: down by 3 percent in the regimen group, up 7 percent in the control group.
The regimen must be followed precisely to achieve its full results, Ornish stresses. Most of the men in the control group tried to follow the regimen, with middling success; their PSA levels rose -- but not as much as would have happened if they had not adopted some of the measures, he maintains.
The study's reliance on PSA levels, however, is seen as a major problem by Andrew Vickers, an assistant attending research methodologist at Memorial Sloan-Kettering Cancer Center in New York.
"When you get down to it, no one should care about the PSA level," he says. "It is widely used, but one has to be cautious in interpreting it. It is a marker of cancer growth, but not necessarily a one-to-one marker."
What Vickers would like to see are measurements of how the cancer is affecting the patients' quality of life. "The results they show are highly provocative, but they are not measuring anything that makes a difference in someone's life," he says.
Dr. B. Jay Brooks, chief of hematology/oncology at the Ochsner Clinic in Baton Rouge, La., also looks at the study with a skeptical eye.
"This was an extremely small study, and the endpoint was a rise in PSA, which is not necessarily related to the progress of the cancer," Brooks says. "The difference between the experimental group and the control group was extremely small and barely reached statistical significance."
It is "an interesting concept," Brooks adds, "but this needs to be expanded to a larger group of patients and followed for a long period of time, perhaps five years."
"If it were me or any of my patients, I would certainly not rely on a change in lifestyle to affect a proven diagnosis," Brooks sums up.