Researchers at the University of Texas Health Science
Center in San Antonio studied 2,779 men without prostate
cancer between 2001-04. In the study released online
Monday in the journal Cancer, they reported finding
that the more obese the men were, the lower their levels
of prostate-specific antigen or PSA. A PSA of 4.0 or
lower usually means no cancer.
Previous studies have shown that prostate cancer is
more aggressive in obese men than in men of average
weight. The researchers wanted to see if the cancer's
detection was somehow being delayed in obese men.
The Texas study found that the most morbidly obese
men had about 30 percent lower PSA levels than men of
normal weight.
"That tells us it's likely or it's possible that prostate
cancer detection may be delayed in overweight or obese
men," said Jacques Baillargeon, associate professor
of epidemiology at the health science center.
The research may encourage many doctors to take a
closer look at the tests of obese men.
"For sure, I will be more vigilant in my patients
who are obese in evaluating their PSA," said Dr. Nelson
Stone of Mount Sinai School of Medicine, who was not
involved in the study. "We may be losing some of the
sensitivity of the test in the obese patient in our
ability to detect prostate cancer. We may have to set
our sights lower."
The antigen used in the screening test is made by
normal prostate cells and is measured in blood. The
higher the antigen level, the more likely the chance
of prostate cancer, as the cells multiply uncontrollably,
according to the American Cancer Society.
But having high PSA levels is not a definitive diagnosis
of cancer, which is why the Atlanta-based society recommends
men with high PSA levels have a biopsy.
The latest study builds on previous research released
in May in the New England Journal of Medicine that found
that men with a "normal" PSA actually had cancer 15
percent of the time and that two-thirds of those men
with cancer had aggressive cases.
The Texas study did not explain why obese men have
lower PSA levels. But doctors believe obese men produce
more estrogen, which drives down testosterone levels
and could affect cells that produce the antigen used
in the test.
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On the Net:
American Cancer Society: http://www.cancer.org
