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Regular Mammograms May Lead to Widespread Overdiagnosis

No significant difference in breast cancer deaths for counties with higher screening, detection rates

MONDAY, July 6, 2015 (HealthDay News) — Increased numbers of small cancers and precancerous lesions are found in geographical areas where more mammograms take place; however, the higher screening rates are not associated with reduced breast cancer mortality, according to a study published online July 6 in JAMA Internal Medicine.

The researchers examined medical data for 16 million women aged 40 and older who lived in 547 counties reporting to Surveillance, Epidemiology, and End Results cancer registries in 2000. Of these women, 53,207 were diagnosed with breast cancer that year and followed for the next 10 years. The study authors then performed a county-by-county comparison of mammogram rates against both the incidence of breast cancer in 2000 and deaths from breast cancer during the follow-up period. The authors specifically looked at the percentage of women aged 40 or older who’d had a mammogram in the past two years.

The researchers found that when breast cancer screening increased by 10 percent, breast cancer was diagnosed 16 percent more often overall. There also was a 25 percent increase in the diagnosis of small breast cancers, which measured 2 cm or smaller. But increased screening did not lead to a significant difference in the number of women who died from breast cancer.

“The simplest explanation is widespread overdiagnosis, which increases the incidence of small cancers without changing mortality,” the authors write.

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