Clinical Decisionmaking

Patients should be involved in prostate cancer screening decisions

Use of the tumor marker prostate-specific antigen (PSA) to test for prostate cancer is controversial for several reasons. First, prostate cancers that will never progress and cause harm are extraordinarily common. That's why even advocates of PSA screening recommend against it in men with less than a 10-year life expectancy (for example, a 75-year-old man in average health).

Due to the lack of data on whether prostate cancer screening does more good than harm, experts disagree on whether it should be done routinely. Owing to this uncertainty, the American College of Physicians-American Society of Internal Medicine recommends that clinicians discuss the pros and cons of prostate cancer screening with male patients in their 50s and 60s.

A reasonable approach is for physicians to share the PSA decision with patients, concludes Michael J. Barry, M.D., of Massachusetts General Hospital. He is principal investigator of the Prostate Patient Outcomes Research Team, which is supported by the Agency for Healthcare Research and Quality (HS08397). In a recent book chapter, Dr. Barry notes that PSA tests can find many cancers earlier than digital rectal examination (DRE), but that DRE does detect tumors missed by PSA testing. In any case, the sensitivity and specificity of PSA measurements are poorly defined.

A large study of "baseline" PSA in banked frozen plasma from men (mean age, 63 years) recruited to the Physicians' Health Study found that the PSA level was elevated at more than 4.0 ng/mL in 73 percent of men who were diagnosed with prostate cancer within the next 4 years and in 46 percent within the next 10 years. In the same study, the PSA level was 4.0 ng/mL or less in 91 percent of men who were not diagnosed with prostate cancer over the next 10 years. Transrectal ultrasonography (TRUS) is insufficiently sensitive and specific to be used as a primary screening test. However, it is commonly used to follow up suspicious DRE or PSA results. TRUS results are then typically followed by prostate biopsies.

See "Nonpalpable prostate cancer," by Dr. Barry, in Black, E., Bordley, D.R., Tape, T., and Panzer, R., editors, Diagnostic Strategies for Common Medical Problems. Philadelphia: American College of Physicians, 1999, pp. 540-548.

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