Overdiagnosis in Breast Cancer Screening: Time to Tackle an Underappreciated Harm

The earlier that cancer is found, the better. This underlying tenet of cancer screening has saved many lives. However, studies are beginning to challenge the certainty that finding cancer early is always better. One stark example was the practice of screening infants for neuroblastoma. After the introduction of a simple urine test in Japan led to nationwide screening, the incidence of neuroblastoma approximately doubled, whereas that of mortality and late-stage disease remained unaffected. Widespread urine testing of infants was subsequently abandoned (1). The excess cases of cancer found on screening were examples of over-diagnosis, defined as occurring when "a condition is diagnosed that would otherwise not go on to cause symptoms or death" (2). Overdiagnosis need not imply that a given screening effort is ineffective or ill-advised. Indeed, overdiagnosis has been documented in effective screening programs for several types of cancer, including breast cancer.