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For the past 25 years, a prostate cancer screening
test called Prostate-Specific Antigen (PSA) has
offered the hope of reducing deaths from prostate
cancer by catching the disease early when cure is
possible. But recent findings have raised concerns
over whether the test’s potential to save some men’s
lives is worth the side effects from unnecessary
treatments it leads to in many men.
Lorelei Mucci, associate professor of epidemiology
at Harvard School of Public Health (HSPH) outlined
the latest research and recommendations on PSA
screening during a lecture at the School on July 30,
2013, part of the annual summer Hot Topics series.
Prostate cancer is the second leading cause of
cancer deaths in US men, after lung cancer. Across
the globe each year, 250,000 men die from the
disease. Routine use of the PSA test has increased
earlier diagnoses of the disease and has likely led
to the observed decreases in prostate cancer
mortality in many Western countries where PSA is
widely used. However, it also has led to a spike in
over-diagnosed tumors that would never cause harm
for a man and would not have otherwise been
identified. These patients then often undergo
difficult treatments that they don’t need and which
can have significant side effects such as erectile
dysfunction and incontinence.
Recommendations from leading medical organizations
regarding which men should be tested and when, and
how to follow-up on an elevated result, are
inconsistent, Mucci said. The US Preventive Services
Tasks force recently reviewed the evidence and came
to the conclusion that there was not sufficient
evidence to support PSA screening to reduce cancer
mortality.
Other groups from the US and Europe recommend that
men be screened starting at ages ranging from 40 to
55.
Others recommend against routine screening for
younger men with only an average risk of dying from
cancer and suggest that the decision whether or not
to screen be an informed choice shared by the
patient and his doctor.
The confusion for doctors and the public comes
primarily from the conflicting data from two large
randomized trials of PSA screening published last
year in The New England Journal of Medicine and
Journal of the National Cancer Institute, with the
first finding that the test reduced prostate cancer
mortality and the second finding that it did not.
Mucci cautioned that the results of these studies
may be premature given the disease’s slow
development. “One of the take-home messages is that
prostate cancer has a long clinical progression,”
she said. “You have to follow men for many years
before you see if they develop metastatic disease [cancer
that spreads beyond the original tumor], and
therefore the results from the screening trials may
become more informative with additional time.”
Little guidance exists for clinicians regarding what
to do if a man’s PSA level is high. At what point
should he receive a biopsy? How often should he be
retested? The answers are unclear as there is no
evidence basis for the decisions, Mucci said.
Combined findings from several recent studies show
that to prevent one death from prostate cancer, 936
men must be screened with the PSA test and 20 to 40
men treated — at a total estimated cost of $5.2
million, Mucci said. But until another biomarker is
found that can detect malignant forms of cancer, men
and their doctors have only the PSA test.
“How do patients and their doctors weigh issues
around impairments in quality of life with potential
death from cancer?” Mucci asked. “How does a doctor
in a 15-minute visit help a man weigh this choice?”
These are some of the key unanswered questions that
men face as they age.
For more information
The New England Journal of Medicine
Prostate-Cancer
Mortality at 11 Years of Follow-up
Journal of the National Cancer Institute
Prostate cancer screening in the randomized
Prostate, Lung, Colorectal, and Ovarian Cancer
Screening Trial: mortality results after 13 years of
follow-up.
Harvard School of Public Health
MDN
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