Routine Mammograms May Overdiagnose Breast Cancer

Routine mammograms do not reduce the incidence of late-stage breast cancer detection and may result in significant overdiagnosis of early breast cancers, according to a study published in the April 3 issue of Annals of Internal Medicine. Some doctors have been expressing concern that such overdiagnosis may cause unnecessary stress and medical procedures, which have risks of their own.

In 1996, Norway began a 10-year rollout of the Norwegian Breast Cancer Screening program for women ages 50 through 69. Researchers analyzed data from 39,888 women with invasive breast cancer; 7,793 had been diagnosed during the screening program. The results showed that an estimated 15 percent to 25 percent of breast cancers (1,169 to 1,948 women) were overdiagnosed.

In addition, the researchers estimated that for every 2,500 women who were invited to be screened, 2,470 to 2,474 will never be diagnosed with breast cancer and 2,499 will never die from breast cancer. On the other hand, six to 10 women will be overdiagnosed and be treated for breast cancer that may never have needed treatment to begin with.

“Mammography might not be appropriate for use in breast cancer screening because it cannot distinguish between progressive and non-progressive cancer,” said lead author Mette Kalager, a visiting scientist at Harvard School of Public Health and a researcher at the Telemark Hospital in Norway.

"Radiologists have been trained to find even the smallest of tumors in a bid to detect as many cancers as possible to be able to cure breast cancer. However, the present study adds to the increasing body of evidence that this practice has caused a problem for women - diagnosis of breast cancer that wouldn't cause symptoms or death."