FRIDAY, Aug. 8 (HealthDay News) -- The standard screening test
for prostate cancer may not be accurate for obese men, leaving them
more vulnerable to the disease, and surgery is less likely to be
effective for them, a new pair of studies found.
"Obese men are more likely to be diagnosed with an aggressive form of the disease," said Dr. Stephen Freedland, an associate professor of urology and pathology at the Duke University Prostate Center, and an author of one of the studies.
The reason: The blood test that looks for elevated levels of the
protein prostate-specific antigen (PSA), indicating a heightened
cancer risk, doesn't seem as reliable for obese men, Freedland
said.
"Our assumption is that these men have more blood volume, so PSA gets diluted, he said. "By the time obese men get to elevated levels, the cancer is more advanced."
The study, published online Friday in the journal
BJU International included nearly 3,400 men who had PSA
tests. The researchers found that the risk of an aggressive cancer
was doubled in obese men diagnosed because of high PSA levels. No
such association was found for obese men diagnosed by a digital
rectal examination, in which the physician feels for an abnormally
large prostate gland.
Prostate cancer is suspected when the PSA reading is 4 or
higher. The current recommendation is for men aged 50 and older to
be offered an annual PSA test, with explanations of its possible
risks and benefits. A federal preventive medicine committee this
week said that PSA screening should not be done for men aged 75 and
older because the risks outweigh the benefits.
"I'm not sure that we should check obese men more often," Freedland said. "But we should have a higher [PSA] index of suspicion of what is not normal -- 3.4 rather than 4; for really obese men, 3.2."
The Duke study measured obesity using body-mass index, which is
a ratio of weight to height. Obesity is defined as a BMI of 30 or
more.
A second report from Duke in the same issue of the journal found
that excess weight influenced the outcome of surgery for prostate
cancer. Men with a BMI of 35 or higher were nearly 60 percent more
likely to have a recurrence of the cancer than thinner men, the
study of 1,434 men found.
One reason is "the difficulty of operating on obese men in
general," said study author Dr. Jayakrishnan Jayachandran, a
urology oncology fellow at the Duke Prostate Cancer Center. "The
prostate is a narrow thing to operate on, and when there is a big
wad of fat in your way, if the abdominal wall is thick, it becomes
a technical issue."
The result is that not all the cancer may be removed, which
means a recurrence after time, Jayachandran said. "The only thing
we can think of is that when you operate on obese people, you have
to be more careful," he said.
The studies results apply to men who might not regard themselves
as obese, Freedland said. "We can't forget that when we use the
term, we are not just talking about very large men," he said. "A
man who is 5 foot 9 and weighs 203 pounds would be considered
obese."
Jayachandran added, "We are not screening these obese men
effectively and are not doing as good a job surgically as could be
done."
More information
To learn more about prostate cancer, visit the
U.S. National Cancer Institute.
