How beneficial is a PSA in screening for prostate cancer?
A few years ago, there was marked disparity among experts as to whether and how screening for prostate cancer should be performed. At that time, the American Cancer Society recommended that the prostate-specific antigen (PSA) blood test and digital rectal exam (DRE) should be done yearly, beginning at age 50, assuming the man had at least a 10-year life expectancy. The US Preventive Services Task Force, on the other hand, believed that the potential harm from PSA testing that included complications from unnecessary biopsies outweighed the potential benefits of detecting early cancer.
There are a number of explanations for why the PSA test is not an ideal screening test for men who are at average risk for developing prostate cancer and who have no symptoms suggesting that they have prostate cancer:
- Prostate-specific antigen (PSA) is a protein produced by both cancerous (malignant) and noncancerous (benign) prostate tissue. PSA is created when the prostate becomes inflamed from a number of causes other than cancer, such as prostatitis and benign prostatic hypertrophy.
- An elevated PSA without the presence of prostate cancer (false positive) often leads to medical procedures with potential risks, worry, and significant financial costs. In particular, the prostate biopsy used to diagnose cancer can cause bleeding and infection.
- Not all men with prostate cancer will have an elevated PSA. Approximately 15% of men with a level below 4 will have prostate cancer on biopsy. Furthermore, if the PSA is in a borderline range between 4 and 10 there is only a 25% chance of having prostate cancer.
- Even when the PSA has accurately detected prostate cancer, the eventual outcome is not necessarily improved. For example, the PSA test may detect small cancers that would never become life threatening since prostate cancer is often slow-growing.
- The reduction in prostate cancer deaths from PSA screening appears to be small, at best. A large U.S. study showed no benefit from screening. A large European study that found the highest reported benefit suggests that no more than 1 man in 1,000 avoids death from prostate cancer because of screening.
With the recent announcement of guidelines from the American Urological Association, the major organizations that are involved with the detection and treatment of prostate cancer are coming closer to consensus regarding their recommendations regarding PSA screening. Remember that these recommendations apply to men who are at low risk and who do not exhibit signs or symptoms of prostate cancer. Older men, African American men, and men who have a family history of prostate cancer have an increased risk of developing prostate cancer. While not just specific for prostate cancer, symptoms suggestive of prostate cancer include trouble urinating, blood in the semen or urine and discomfort in the pelvic area.
PSA Screening Recommendations:
- The US Preventive Services Task Force recommends against PSA-based screening for prostate cancer regardless of age. They have found with moderate to high certainty that PSA testing has no net benefit and that the potential harms from screening outweigh benefits. Again, this recommendation does not include the use of PSA testing for surveillance after diagnosis or treatment of prostate cancer.
- The latest recommendations from the American Urologic Association are as follows:
- PSA screening in men under age 40 years is not recommended.
- Routine screening in men between ages 40 to 54 years at average risk is not recommended.
- For men ages 55 to 69 years, the decision to undergo PSA screening involves weighing the benefits against the known potential harms associated with screening and treatment. For this reason, shared decision-making is recommended for men age 55 to 69 years that are considering PSA screening, and proceeding based on patients’ values and preferences.
- To reduce the harms of screening, a routine screening interval of two years or more may be preferred over annual screening in those men who have participated in shared decision-making and decided on screening. As compared to annual screening, it is expected that screening intervals of two years preserve the majority of the benefits and reduce over diagnosis and false positives.
- Routine PSA screening is not recommended in men over age 70 or any man with less than a 10-15 year life expectancy.
- The American Cancer Society recommends men learn as much as they can about prostate cancer screening risks and benefits and discuss the information with their doctor before deciding whether to be tested at all. Men at average risk of prostate cancer should have this discussion starting at age 50. Men at higher than average risk (African Americans and those with first-degree relatives who had prostate cancer at an early age, in particular) should have the discussion starting at age 40 or 45.
While the recommendation to avoid the use of routine PSA screening from various medical authorities is reaching consensus, these groups are also aware that better, more specific tests are needed to screen for this common form of cancer.
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