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 mammog
All rights reserved