Experts divided on prostate screening for obese men

Medical Tribune October 2008 SFXVII
David Brill

A new study from the US has prompted
debate among urologists about how
best to screen obese men for prostate cancer.
The research in BJU International concluded
that prostate-specific antigen (PSA)
screening is less effective at detecting cancers
in the obese, who typically experience
more aggressive disease than men of normal
weight.
Lead author Professor Stephen Freedland,
from the Duke University Medical
Center, US, said that obese men have lower
PSA levels and the screening threshold
should therefore be lowered accordingly.
However one of Singapore’s leading
urologists disagreed with the conclusions of
the study and said that he would not adjust
screening practices for obese patients.
Freedland et al. conducted a retrospective
analysis of two different patient databases,
identifying a total of 3,389 cases of
prostate cancer treated by radical prostatectomy
(RP) between 1988 and 2007. [BJU Int
2008 Aug 7; Epub ahead of print]
They found that high BMI was linked to
poor outcomes after RP in patients whose
prostate cancer was detected by PSA screening
but not among those whose cancer was
detected by digital rectal exam.
Worse outcomes were only evident,
however, among PSA-detected cancers that
were treated since 2000. Obesity was not
significantly associated with cancer recurrence
for those treated before 2000.
“I’m personally using a lower PSA
threshold for obese men,” said Freedland.
“Whatever you would use, it should probably
be somewhere between 10 to 20 percent
lower for obese men, depending on the
degree of obesity.”
Associate Professor Kesavan Esuvaranathan,
a senior consultant at National University
Hospital in Singapore, said however
that the data from the study do not provide
a statistically sound method for determining
the PSA cut-offs for obese men.
“I will continue to use 4 ng/ml as a
standard cut-off and a sharp increase in
PSA velocity for patients who are already
on follow-up, as triggers for a prostate biopsy.
In patients with PSA in the 4 to 10 ng/
ml range, I would also use free and/or total
PSA as a guide in management,” he said.
Esuvaranathan, who is president of the
Singapore Urological Association, said that
there may be many different causes for the
poor outcomes seen among obese men with
prostate cancer.
“It is not quite true that the year 2000
is an adequate cut-off point ... PSA testing
has been in use in the US from the early 90s
and I’d like to see the data that shows that
the intensity of screening increased at this
somewhat arbitrary time point,” he added.
Freedland said that the lower PSA values
seen in obese men could result from
their increased blood volume, which could
dilute the blood and give lower PSA measurements.
The same adjustment principle
could apply when screening for any tumorderived
cancer marker, he added.
A second paper by Freedland and colleagues
linked obesity to increased positive
surgical margins following RP, suggesting
that this surgery is more difficult in obese
patients. [BJU Int 2008 Aug 6; Epub ahead
of print]