JAMA: Mammography does not reduce breast cancer deaths, could result in overdiagnosis

As physicians turn to mammography as a more reliable way to diagnose breast cancer, a new study shows that the screening method does not reduce the number of deaths from the disease and could lead to overdiagnosis, suggesting a few kinks in the system.

Researchers gathered data from the Surveillance, Epidemiology and End Results (SEER) cancer registries, which includes more than 16 million women aged 40 or older from 547 counties in the U.S. About 53,207 of the women were diagnosed with breast cancer during a 12-month period and had follow-ups over the next 10 years. Scientists looked at the rate of breast cancer screening for each county, zeroing in on the percentage of women who had a mammogram during a two-year period, and also analyzed the number of breast cancer cases and deaths from the disease.

The team found that while there was a 10% jump in breast cancer screening and a 16% rise in breast cancer diagnosis, the death rate remained the same. The 10% increase in breast cancer screening was linked to a 25% rise in small breast cancers, or tumors that are 2 cm or less, Medical News Today reports.

And more breast cancer screening did not necessarily cut down on large breast cancers. Although researchers saw increased rates of mammography, it was linked with a 7% jump in larger breast cancers. Scientists published their findings in a recent issue of JAMA Internal Medicine.

"What explains the observed data? The simplest explanation is widespread overdiagnosis, which increases the incidence of small cancers without changing mortality, and therefore matches every feature of the observed data," study co-author Richard Wilson of Harvard University said in a discussion of the study.

Still, doctors should view the data with a wary eye, researchers said in an accompanying editorial. The study does not take into account whether the people who received mammograms actually developed breast cancer, whether the testing or the onset of the disease came first, or if there are other explanations for the findings, researcher Joann Elmore of the University of Washington said. The best route for physicians to take is to improve their communication with patients about potential screening methods.

"In the end, we all need to become comfortable with informing women that we do not know the actual magnitude of overdiagnosis with precision. Part of informed decision making is providing all the information, even our uncertainty," Elmore said, as quoted by MNT.

- read the JAMA Internal Medicine study abstract
- here's the Medical News Today article
- get more from MNT