Mammograms Every Other Year OK for Women Over 50: Study

In 2009, the U.S. Preventive Services Task Force, an independent panel of experts, issued its guidelines that women 50 to 74 at average risk should get a mammogram every two years. Women 40 to 49, the task force said, should talk with their doctor about the risks and benefits of screening.

The task force guidelines are at odds with those of many other organizations, including the American Cancer Society, which recommends annual screening beginning at age 40.

The task force guidelines consider only a woman's age, according to Kerlikowske. Her team decided to study the benefits and harms of screening based not just on age but also on breast density and hormone therapy use.

Women in the study were 40 to 74. Most diagnosed with breast cancer during the years studied, 1994 to 2008, were 50 or older. They typically had dense or very dense breasts.

The study has flaws, said Dr. Daniel Kopans, a professor of radiology at Harvard Medical School and senior radiologist in the breast imaging division of Massachusetts General Hospital. He is also a member of the American College of Radiology's Breast Imaging Commission.

The groups weren't identical, he said, and that would have been the best way to study the issue. Information is lacking, too, he said, on why some women got screened annually and others did not. "Those screened every year may have had different risk factors," he said.

"I would tell women it makes sense to get screened every year," Kopans said.

In a statement, the American College of Radiology (ACR) pointed to an analysis published in 2011 in the American Journal of Roentgenology finding that under the biennial model, about 6,500 more women annually in the United States would die of breast cancer.

Looking at early versus late-stage cancer is not the best way to judge the best interval for mammograms, according to the ACR statement. Rather, it said, researchers should look at such factors as tumor size and other markers of detecting cancers early.

Dr. Robert Smith, senior director of cancer screening for the American Cancer Society, said that the study is "not an accurate look at one year versus two years." For the study, annual was defined as intervals of nine to 18 months, for instance, and two years as more than 18 to 30 months.

Kerlikowske, in response, said this interval variability reflects real life.

Despite that criticism, Smith said the type of individualized screening studied in the new research is the direction that cancer prevention is headed. "If we can identify more clearly not only who will and who will not get cancer, but what those screening intervals are and if they can be screened safely at a longer interval, that would be good," he said.

"Some day we may be able to say certain women can have longer intervals," Smith said.

SOURCES: Karla Kerlikowske, M.D., professor of medicine, epidemiology and biostatistics, School of Medicine, and Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; Daniel Kopans, M.D., professor of radiology, Harvard Medical School, and member, American College of Radiology Breast Imaging Commission, and senior radiologist, breast imaging division, Massachusetts General Hospital, Boston; March 18, 2013, statement, American College of Radiology; February 2011, American Journal of Roentgenology; March 18, 2013, JAMA Internal Medicine, online