Overdiagnosis and mammography screening

The NHS recently scrapped its leaflet inviting women to undergo mammography in response to criticisms that it failed to mention the major harm of screening—overdiagnosis.1 In the linked systematic review (doi:10.1136/bmj.b2587), Jørgensen and Gøtzsche provide evidence that screening has led to overdiagnosis of breast cancer not only in the United Kingdom, but also in Canada, Australia, Sweden, and Norway.2

Overdiagnosis refers to the detection of abnormalities that will never cause symptoms or death during a patient’s lifetime. Overdiagnosis of cancer occurs when the cancer grows so slowly that the patient dies of other causes before it produces symptoms or when the cancer remains dormant (or regresses). Because doctors don’t know which patients are overdiagnosed, we tend to treat them all. Overdiagnosis therefore results in unnecessary treatment.

With the advent of widespread efforts to diagnose cancer earlier, overdiagnosis has become an increasingly vexing problem. Overdiagnosis is a widely recognised problem in prostate cancer screening, and it …