Why Obese Men Post Lower PSA Levels(d. It's like taking a little bit of a d...),Health

The study authors looked at the records of about 14,000 men with prostate cancer who underwent removal of their prostates between 1988 and 2006. The findings are published in the Nov. 21 issue of the Journal of the American Medical Association.

The researchers found that men who were fatter had larger blood volumes, which the study authors said supports their theory that dilution caused their PSA levels to lower.

The same thing could hold true for blood markers of other cancers, Freedland said. "As we develop blood tests for other cancers, we should be keeping this in mind," he added.

However, Dr. Nelson Stone, a clinical professor of urology and radiation oncology at Mount Sinai School of Medicine, is skeptical of the results, because the research just focused on men with advanced prostate cancer. That and other factors may have skewed the results, he said.

"I don't think they've proved their point," he said. But he added, "We need to be a little bit more careful when we evaluate a patient who is larger, and we look at his PSA and compare to a patient who is thinner. The PSAs are not the same."

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SOURCES: Stephen Freedland, M.D., urologist and assistant professor, urology and pathology, Duke Prostate Cancer Center, Durham, N.C.; Nelson Stone, M.D., clinical professor, urology and radiation oncology, Mount Sinai School of Medicine, New York City; Nov. 21, 2007, Journal of the American Medical Association