At what age should women undergo breast cancer screening mammography—and how often?

Providing an answer to these questions is growing increasingly important in light of a recent study that concluded “widespread overdiagnosis” of breast cancer has resulted from screening mammography, with no significant difference in the overall death rate.

The study, published in JAMA Internal Medicine, looked at the extent of breast cancer screening among 16 million women ages 40 and older who lived in 547 United States counties reporting to the Surveillance, Epidemiology, and End Results cancer registries during the year 2000; breast cancer incidence in the year 2000; and incidence-based deaths from breast cancer during a 10-year follow-up.1

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Counties with the highest number of screenings had 1.8 times more breast cancer diagnoses than those with the least screening, said Charles Harding, AB, currently in private practice in Seattle, WA, in a podcast interview on the JAMA Network.

RELATED: Breast Cancer Overdiagnosis, False Positives Linked with High Cost

The relationship between breast cancer diagnoses and screening mammography for tumors less than 2 cm at diagnosis showed that there were 2.2 times as many tumors being diagnosed in the counties with the most screening. For larger tumors, there was little association and between early screening and reduction in the rate of breast cancer diagnosis, Harding said.

“This tells us that the potential for overdiagnosis is very high,” he added. “Overdiagnosis was perhaps the clearest result of screening when analyzed at the population level and was much clearer than any potential reductions in tumor size at diagnosis.”

The U.S. Preventive Services Task Force (USPSTF) calls overdiagnosis the most serious harm of screening mammogram, defining it as diagnosis and treatment for a type of breast cancer that would not have become a threat to a woman’s health during her lifetime. In addition, “the most common harms of screening mammography are false–positive screening exams leading to additional tests and procedures,”2 the USPSTF noted.

Joann G. Elmore, MD, MPH, professor of medicine and adjunct professor of epidemiology at the University of Washington School of Medicine in Seattle, WA, who wrote a commentary on the study in JAMA Internal Medicine, told Cancer Therapy Advisor that “this article adds to a growing body of evidence suggesting that breast cancer screening has less benefit than we had hoped for and that potential harms, such as overdiagnosis, need to be acknowledged.”