The false positive paradox regarding prostate cancer
Let’s first, as an illustration of the issue, look at the history of screening for prostate cancer. In the U.S. screening for prostate cancer was normal practice, under the common sense notion that it is good to detect and treat illnesses early. What resulted, however, was a high level of false positives due to the false positive paradox, and a growing awareness that most prostate cancers don’t grow fast enough to be an issue for the patient, particularly in the elderly.
Consequently, the CDC, American Cancer Society, American Medical Association, and most other groups have stopped recommending widespread testing for prostate cancer, due to potential for false positives, overdiagnosis, overtreatment, and possible iatrogenic harm. CDC, for example, states at its prostate cancer website (CDC Prostate Cancer website, emphasis in original):
Possible Harm from Screening: False positive test results: This occurs when a man has an abnormal PSA test but does not have prostate cancer. False positive test results often lead to unnecessary tests, like a biopsy of the prostate. They may cause men to worry about their health. Older men are more likely to have false positive test results. Possible Harms from Diagnosis: Screening finds prostate cancer in some men who would never have had symptoms from their cancer in their lifetime. Treatment of men who would not have had symptoms or died from prostate cancer can cause them to have complications from treatment, but not benefit from treatment. This is called overdiagnosis.