Jan. 24 (Bloomberg) -- Severely overweight men may not get accurate results from early screenings for prostate cancer, a new study suggests.

Men who were overweight for their height were less likely to show warning signs of cancer in a standard test for prostate- specific antigen, or PSA, according to a study published in the journal Cancer. High PSA levels often indicate a high risk of prostate cancer, the second-most deadly form of the disease among men.

``An overweight or obese man may have an artificially low PSA,'' said Ian Thompson of the University of Texas Health Science Center in San Antonio, and the study's author.

In a study of 2,770 men, those with a higher body mass index -- or weight-to-height ratio -- had proportionally lower PSA scores although earlier research links high body mass to advanced stages of prostate cancer and low survival rates. These findings, published in the March 1 edition of Cancer, suggest that screening alone may be an imprecise indicator for certain patients.

In obese patients, or those with a body mass index of 30 or greater, lower testosterone levels may prevent normal PSA levels and may hide the disease from diagnosis, Thompson said in an interview.

Further Testing

Thompson said further studies will measure the effectiveness of PSA tests, such as those manufactured by Illinois-based Abbott Laboratories and California-based Beckman Coulter Inc., in screening for prostate cancer. Family history, race, body mass index and other factors should also be considered when assessing cancer risk, he said.

The American Cancer Society estimates that about 30,000 men die annually in the U.S. of prostate cancer, and an estimated 232,000 new cases will be diagnosed this year, according to a report released last week.

Obesity has been associated with a higher risk of developing several diseases, including diabetes, heart disease and certain forms of cancer.

The study was sponsored by a grant from the National Cancer Institute. The journal Cancer is published by the American Cancer Society.

To contact the reporter on this story: Catherine Larkin in Princeton at clarkin4@bloomberg.net.

Last Updated: January 24, 2005 00:26 EST