Yearly mammogram after 40 has high rate of false alarms: Study

By Dr. Ananya Mandal, MDOct 18 2011

Latest evidence suggests that getting a mammogram each year after age 40 may not be a good idea. A study suggests that far fewer women would be put through the anxiety of being called back for a second mammogram and unnecessary biopsies if screening took place every two years.

The study published Monday in the Annals of Internal Medicine, consisted of data from more than 169,000 women age 40 to 59. Researchers led by the Group Health Research Institute in Seattle found that in 10 years of annual screening, 61% of the women will be called back for another mammogram screening because the first reading was inconclusive. About one in 12 women will be referred for a “false positive” biopsy. On the other hand when screening occurred every other year, about 42% of women were called back for another mammogram.

“What we found was more than half of women participating in annual screening would have a false positive after 10 years,” Rebecca Hubbard of the Group Health Center for Health Studies in Seattle, said. “The risks (of a false positive) are decreased by a third with biannual screening compared to annual after 10 years,” Hubbard said.

The researchers add that having prior year mammograms available made a big difference in reducing false positive readings. Thus women should try to have their mammograms taken at the same place each time or, if they switch sites, order their previous mammograms sent to the new office.

Annual screening also did not greatly affect breast cancer severity. Among women diagnosed with cancer, those screened at two-year intervals were only slightly more likely to be diagnosed with advanced disease compared with those screened yearly.

”Women and physicians should be aware of the possibility of these harms associated with different screening intervals so they can make informed decisions about screening and be prepared for what to expect when they receive their results,” the authors wrote. Hubbard said the findings should be used by doctors to help women them make an informed decision about screening mammograms.

In 2009, the U.S. Preventive Services Task Force, a government-backed advisory panel, issued new guidelines that suggested women should start routine mammograms at age 50 rather than 40, in part because the tests have such high false positive rates and the benefits in lives saved did not outweigh the worry and anguish caused by the false positive results. Many groups, including the American Cancer Society, have stuck by their long-standing recommendations of a yearly breast exam for women starting at age 40, stressing that the breast X-rays have been proven to save lives by spotting tumors early, when they are most easily treated.

In another study in the same issue of the journal researchers compared digital versus traditional film mammography and found little difference in breast cancer detection rates in women age 50 to 79. However, women age 40 to 49 with dense breasts may benefit from digital mammography, the authors said.