Overdiagnosis more likely than early detection of threatening cancer with mammography screening

Overdiagnosis of breast cancer has been suggested on the basis of multiple studies that used different designs and approaches and is acknowledged by national organizations such as the American Cancer Society and the U.S. Preventive Services Task Force. Although Dr. Welch and his associates present powerful data on a large number of women in a very clear fashion, they also rely on data with extensive missing values, make assumptions about underlying disease burden that cannot be verified, and acknowledge that their estimates are imprecise.

Rather than focusing on statistical issues and study design, we should move forward by agreeing that overdiagnosis does occur, even though the exact percentage of overdiagnosed cases remains unknown. Some consider overdiagnosis to be an intractable problem. No single approach will adequately address the issue. Instead, a multilevel approach ranging from research and education at the population level to intensified focus at the patient level is needed. One way to reduce overdiagnosis is targeted, precision screening of persons who have a higher risk of breast cancer rather than screening large populations in which the majority of persons are at a lower risk for harmful disease.

At the provider level, we need better tools to evaluate medical data and classify findings on the basis of clinical judgment. Previous research has documented extensive diagnostic variability among radiologists in their interpretation of mammograms and among pathologists in their interpretation of breast biopsy specimens. We are using archaic disease-classification systems with inadequate vetting and defective nosologic boundaries. Diagnostic thresholds for “abnormality” need to be revised because the middle and lower boundaries of these classification systems have expanded without a clear benefit to patients.

Rigorous analytic methods are required for the development of disease nosologies, and physicians need more sophisticated tools to improve diagnostic precision and accuracy. At the patient level, we need better methods of distinguishing biologically self-limited tumors from harmful tumors that progress. We must also improve communication regarding overdiagnosis at all levels, from dissemination of scientific findings at a population level to education of patients before they undergo screening.

Clinicians face time constraints and lack experience in communicating screening nuances. Better training may help. Building trust in science and medicine starts by taking ownership of all aspects of the screening cascade, including the collateral damage of our well-intentioned efforts.

Dr. Elmore is a professor of medicine and adjunct professor of epidemiology at the University of Washington. Dr. Elmore reported having no relevant disclosures related to this commentary but did report receiving financial compensation from UpToDate and Healthwise/Informed Medical Decisions Foundation. These comments are excerpted from an accompanying editorial (N Engl J Med. 2016 Oct 12;375[15]:1483-6).