Patients as well as medical professionals are debating prostate cancer screening.
Several recent studies have shown that diagnosed cases of prostate cancer have decreased over several years, with a reduction in screening for the prostate cancer marker, PSA. In 2015, 220,000 new cases of prostate cancer were diagnosed with almost 28,000 deaths.
As with mammography for breast cancer, advocates insist prostate cancer screening saves lives while detractors argue it leads to too much unnecessary treatment. I would argue a middle ground that the two opposing camps may both agree to.
Clearly, too much screening has occurred in the past. The medical community now realizes that many prostate cancers do not grow very quickly, and they are unlikely to affect a man’s lifespan. More and more of these cases are simply monitored.
But a set of aggressive cancers do progress quickly. In these cases, screening does save lives. The importance of screening these high-risk cancers was demonstrated in two large studies that followed patients for more than 12 years. Regardless, the identification of these cancers requires PSA screening as an entry point.
Also, it’s very unlikely that men with less than a 10- to 15-year life expectancy will benefit from PSA screening. This was emphasized in a recent study examining treatment versus non-treatment of slow growing prostate cancer.
Therefore, many older men and those with significant health problems should not get PSA screening.
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Fortunately, we can improve the deployment of PSA testing in several ways:
- Recent data suggest that using an interval of two years or longer may be preferred over annual screening.
- Using an improved PSA measurement (the free-to-total PSA ratio) adds specificity to the test and helps men avoid unnecessary biopsies.
- Finally, it may be possible to individualize PSA screening strategies by quantifying baseline risk for high-risk prostate cancer. A single PSA of less than 1 ng/ml at age 50 is associated with a six-fold lower risk of dying of prostate cancer. So PSA can be treated to a certain extent like a colon cancer screening. Men identified as low-risk can simply get a PSA every 10 years. By using a more strategic approach, maximizing benefits while minimizing harm, some of the false positives leading to overtreatment can be decreased.
The decline of prostate cancer screening is of concern, especially in light of a major U.S. screening trial being invalidated recently, according to the New England Journal of Medicine. This trial, which made a mistake in tracking how many participants had been screened, had been the basis of the United States Preventive Health Services Task Force criticism of PSA screening. I would argue a reevaluation of the strengthening data for screening is due.
PSA is not a perfect test and the hunt is on for new approaches. Investigation into other blood tests is encouraging, and research using urine as a detection source is ongoing here at the University of Wisconsin Carbone Cancer Center and other institutions. We know a more specific marker exists for detecting just the high-risk prostate cancers.
While in the past, physicians and patients have been overly aggressive in their approach to screening, I am concerned that the pendulum may be swinging back too far the other way. This is a health issue that is becoming increasingly important as the population ages.
By approaching men in a more tailored fashion, many of the critiques of PSA screening may be addressed while also improving survival outcomes for those men who would benefit from screening.