Strategies needed to address breast cancer overdiagnoses
MedWire News: Many breast cancers detected by screening tests are not destined to cause symptoms or death and therefore represent overdiagnosis, say researchers.
Because overdiagnosis leads to unnecessary treatment and associated harms, it is important to develop clinical and research strategies to recognize, quantify, and manage it, according to the authors of a review published in the Journal of the National Cancer Institute.
Gilbert Welch (Department of Veterans Affairs Medical Center, White River Junction, Vermont, USA) and William Black (Dartmouth–Hitchcock Medical Center, Lebanon, New Hampshire, USA) used existing data from large randomized screening trials to estimate the extent of overdiagnosis in several cancers.
For breast cancer, only the 10-year Malmö mammographic screening trial reported long-term follow-up data on incident cancers. In this trial, the authors estimated that 24% of 477 mammographically detected breast cancer represented overdiagnosis.
The authors also point to cancer incidence and mortality statistics as evidence of overdiagnosis. Surveillance Epidemiology and End Results data from 1975 to 2005 show a slight decline in breast cancer death, likely attributable to improved screening and treatment, and reduced use in hormone replacement therapy. But this is paralleled with a steep increase in diagnoses, leaving little doubt that overdiagnosis is occurring.
“To address the problem, patients must be adequately informed of the nature and the magnitude of the trade-off involved with early cancer detection,” write Welch and Black.
For example, physicians could explain that for every 50-year-old woman who avoids a breast cancer death, between two and 10 women will be overdiagnosed and treated needlessly, and between 50 and 200 women will be biopsied unnecessarily.
“Equally important, researchers need to work to develop better estimates of the magnitude of overdiagnosis and develop clinical strategies to help minimize it,” say the authors.
In an accompanying editorial, Laura Esserman (University of California, San Francisco, USA) and Ian Thompson (University of Texas Health Science Center, San Antonio, USA) stress the importance of addressing the problem of overdiagnosis.
"What we need now in the field of cancer is the coming together of physicians and scientists of all disciplines to reduce the burden of cancer death and cancer diagnosis," they write. "We must advocate for and demand innovation in diagnosis and management, fueled by science, harnessing modeling, molecular, and immunology tools to address this problem."
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By Laura Dean