FRIDAY, Jan. 6 (HealthDay News) -- Annual screening for prostate
cancer doesn't save lives, finds a new study that is unlikely to
quell the controversy surrounding routine prostate specific antigen
"Organized prostate cancer screening when done in addition to whatever background testing exists in the population does not result in any apparent benefit, but does result in harm from false positives and over-diagnosis," said lead researcher Philip Prorok, from the Division of Cancer Prevention at the U.S. National Cancer Institute.
"Men considering prostate cancer screening should be fully informed of the implications of such testing before making a decision," he added.
Experts have disagreed for some time on whether the blood test
saves lives or results in over-diagnosis and over-treatment. The
new findings, which extend prior results out to 13 years of
follow-up, are published in the Jan. 6 online edition of the
Journal of the National Cancer Institute.
The study followed men enrolled in the Prostate, Lung,
Colorectal and Ovarian Cancer Screening (PLCO) Trial from 1993 to
2009, comparing results for a group of men who had undergone
screening with those for men who hadn't had testing. The men were
55 to 74 years old.
One group had PSA screening every year for six years and a
digital rectal examination every year for four years. The other men
had regular care, which in some cases included screening if
requested by the patient or doctor.
Compared to men getting usual care, the screened men had a 12
percent relative increase in prostate cancer but a slightly lower
rate of high-grade cancer.
However, no difference in deaths was seen between the two
This finding held true even after age, screening before the
trial and other medical conditions were taken into account, the
Prorok said that better treatment for prostate cancer may
explain the similar mortality results.
Among prostate cancer patients, death from other causes was
somewhat higher in the screened group (10.7 percent of 4,250 men
with prostate cancer) compared to the usual care group (9.9 percent
of 3,815 men with prostate cancer).
This indicates men who underwent PSA screening were
over-diagnosed, meaning the test picked up slow-growing tumors that
probably weren't lethal, the researchers said.
"PSA testing and digital rectal examination screening as conducted in this trial did not reduce prostate cancer mortality, but there was a persistent excess of prostate cancer cases in the screened arm, suggesting over-diagnosis of prostate cancer," Prorok said.
Some prostate cancer experts disagree with the authors'
Dr. Anthony D'Amico, chief of radiation oncology at Brigham and
Women's Hospital in Boston, said the results are invalid because
the trial was flawed.
According to D'Amico, 52 percent of those who received usual
care had a PSA screening. "That's a serious issue which makes it
very hard for the study to show if any benefit exists for PSA
screening," he said.
Also, 15 percent of those who were supposed to get PSA screening
never did, D'Amico said. "So what you've got is a screening study
in which 85 percent of the people got PSA screened on the screening
arm and 52 percent got screened on the control arm, which makes it
impossible to ever measure a difference," he said.
Men should ignore this study, "because it has no relevance to
PSA screening," D'Amico said.
D'Amico said he has more confidence in the results of a European
study published in 2009 in the
New England Journal of Medicine, which showed a 20 percent reduction in cancer mortality with PSA screening.
Men who can benefit most from screening are those at risk for
prostate cancer, particularly men who have a family history of
prostate cancer, African Americans and men over 60, D'Amico
Prorok acknowledged that the PLCO trial wasn't perfect.
"Nonetheless, the contamination was not enough to eliminate the
early diagnosis of prostate cancers nor the persistent excess of
cancers," he said.
PLCO provides information about over-diagnosis, Prorok added.
"Even if the contamination did dilute a benefit compared to no
screening, the result of no mortality difference between the arms
in PLCO could be interpreted to suggest that more intensive
screening is not beneficial but does result in harm," he said.
For more information on prostate cancer, visit the
American Cancer Society.
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