Could PSA Screening Be Harmful? New Guidelines Available
Abstract & Commentary
By Rahul Gupta, MD, MPH, FACP, Assistant Professor, Department of Internal Medicine, Meharry Medical College, Nashville, TN; Assistant Clinical Professor, Division of General Internal Medicine and Public Health, Vanderbilt University Medical School, Nashville, TN. Dr. Gupta reports no financial relationship to this field of study.
Synopsis: Whereas its potential benefits remain uncertain, prostate-specific antigen (PSA) screening may be associated with psychological harms. There has been a recent update to the screening guidelines by the U.S. Preventive Services Task Force (USPSTF).
Source: Lin K, et al. Benefits and harms of prostate-specific antigen screening for prostate cancer: An evidence update for the U.S. Preventive Services Task Force. Ann Intern Med 2008;149:192-199 (Summary for patients available at: www.annals.org/cgi/content/summary/149/3/185).
Among U.S. men, prostate cancer is the most common non-skin cancer. According to the National Cancer Institute's data from 2003 to 2005, 15.78% of men born today will be diagnosed with prostate cancer at some time during their lifetime.1 Also, 8.04% of men will develop cancer of the prostate between their 50th and 70th birthdays. About 91% of prostate cancer cases are diagnosed while the cancer is still confined to the primary site or after the cancer has spread to regional lymph nodes (localized or regional stage). At any time, there are more than 2 million men carrying a diagnosis of prostate cancer in the United States. In 2006, the American Cancer Society estimates that 27,350 men died of prostate cancer.2
Although its application was approved by the FDA in 1986, the PSA test is non-specific for prostate cancer as other conditions such as benign prostate hyperplasia or prostatitis can also raise its levels. Therefore, prior to issuing its recommendations in 2002, the USPSTF could not find firm evidence of effectiveness linking screening to improved health outcomes.3 The USPSTF also noted that the balance of potential benefits and harms of early treatment of the types of cancers found by screening remained uncertain. Therefore, the recommendation at the time was that there was insufficient evidence to recommend for or against routine PSA testing.
The current study by Lin and his colleagues examined new evidence available from 2002 to 2007 to evaluate the benefits and harms of PSA screening in men. Utilizing PubMed, they attempted to answer three key questions: Does screening for prostate cancer with PSA, as a single-threshold test or as a function of multiple tests over time, decrease morbidity or mortality? What are the magnitude and nature of harms associated with prostate cancer screening, other than over-treatment? What is the natural history of PSA-detected, non-palpable, localized prostate cancer?
What the authors found was somewhat revealing in that no good-quality randomized, controlled trials of screening for prostate cancer have been completed. There was no good evidence available to demonstrate a mortality benefit from PSA screening. However, in one cross-sectional and two prospective cohort studies of fair to good quality, there was evidence to suggest that false- positive PSA results caused psychological adverse effects for up to one year after the test. Additionally, no population-based studies were found that determined the health outcomes resulting from natural progression of an early stage disease. The authors concluded that PSA screening is associated with psychological harms while its potential benefits remain uncertain.
Commentary
Despite its lack of efficacy and resultant lack of recommendation, PSA as a screening test remains quite popular among primary care clinicians. When applying a screening test to a population or a community setting, the intention is to identify the disease early, thus enabling earlier intervention and management with intent to reduce mortality and/or morbidity. Intuitively, screening makes sense because if one can catch a disease process earlier, more can be done about it. However, such may not always be true. Inappropriate application of a screening test may lead to more false positives with resultant adverse effects like psychological effects, harm from further confirmatory testing, and over-utilization of the existing health care resources.
For a screening test to be successfully applicable to populations, the following criteria must be met: The condition should be an important health problem with available treatment to affect the earlier diagnosis; the testing should be able to detect the disease in an earlier stage; the testing method should be acceptable to researchers and the population; the natural history of the disease should be clearly understood; and case-finding should be cost-effective.4 With PSA screening for prostate cancer, many patients are identified that would otherwise not develop any problems from it. This is termed "overdiagnosis bias." Another issue is that it is unclear if there is any benefit in treatment of prostate cancer at the earliest stages. Therefore, PSA screening in men at late age (>75 years) may detect cancers that would not have killed the patient or even been detected prior to death from other causes. This is termed "length time bias." On the other hand, many individuals who undergo earlier diagnosis and treatment for prostate cancer due to the available PSA screening also develop harms such as erectile dysfunction, urinary incontinence, bowel dysfunction, and rarely death.
As a result, the USPSTF recently revised its guidelines.5 The USPSTF concluded that current evidence is insufficient to assess the balance of benefits and harms of prostate cancer screening in men younger than age 75 years. It further recommended against screening for prostate cancer in men age 75 years or older. In men younger than age 75 years, the USPSTF could not determine the net benefit of screening because of low certainty about the magnitude of benefits of screening and treatment.
What would I do? As a primary care physician, in patients 50-74 years, I would discuss the potential benefits and known harms of PSA screening with my patients, consider their preferences, and together come to a conclusion on an individual basis. However, in those who are at increased risk (African American men and men with family history of a first-degree relative with prostate cancer), I would recommend PSA screening starting at age 45 years.
References
1. National Cancer Institute Surveillance Epidemiology and End Results Program. Cancer Stat Fact Sheets, cancer of the prostate. Available at: http://seer.cancer.gov/statfacts/html/prost.html. Accessed Aug. 27, 2008.
2. Jemal A, et al. Cancer statistics, 2007. CA Cancer J Clin 2007;57:43-66.
3. Harris R, Lohr KN. Screening for prostate cancer: An update of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2002;137:917-929.
4. World Health Organization Principles and Practice of Screening for Disease. Available at: http://whqlibdoc.who.int/php/WHO_PHP_34.pdf. Accessed Aug. 27, 2008.
5. U.S. Preventive Services Task Force. Screening for Prostate Cancer: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med 2008;149: 185-191.
Whereas its potential benefits remain uncertain, prostate-specific antigen (PSA) screening may be associated with psychological harms. There has been a recent update to the screening guidelines by the U.S. Preventive Services Task Force (USPSTF).You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content