Mammograms and prostate-specific antigen (PSA) tests have led to especially high rates of overdiagnosis and overtreatment for breast and prostate cancer. A 2013 meta-analysis by the Cochrane Collaboration, an international association of experts that assesses medical procedures, estimated that if 2,000 women have mammograms over a period of 10 years, one woman’s life will be saved by a positive diagnosis. Meanwhile 10 healthy women will be treated unnecessarily, and more than 200 “will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.”
Another nonprofit medical group, theNNT.com, has spelled out a disturbing implication of these data. (NNT stands for “number needed to treat,” which refers to the number of people who must receive a treatment for one person to receive any benefit. Ideally, the number is 1.) The NNT notes that some overdiagnosed women might “die due to aggressive therapies such as chemotherapy and major surgery.” Thus any benefit from screening “is balanced out by mortal harms from overdiagnosis and false-positives.” Breast-cancer specialist Michael Baum, who helped found the United Kingdom’s breast-screening program, has advocated abandoning such programs, which he believes might cut short more lives than they extend.
As for PSA tests, a federal task force of medical experts estimates that 1.3 deaths may be averted for every 1,000 men between the ages of 55 and 69 tested for 13 years. But for every man whose life is extended, many more will experience “false-positive results that require additional testing and possible prostate biopsy; overdiagnosis and overtreatment; and treatment complications, such as incontinence and erectile dysfunction.” A 2017 analysis by the task force estimated the ratio of beneficial PSA tests to false positives and overdiagnosis to be as high as 1/240.
A 2013 meta-analysis by Cochrane Group found “no significant reduction” in mortality resulting from PSA tests. “The strategy of routinely screening all men with PSA tests leads to interventions that are not saving lives and may be causing harm,” the NNT stated. The discoverer of the prostate-specific antigen, pathologist Richard Ablin, has called the PSA test a “profit-driven public health disaster.”