Mammograms Less Effective Than Believed
Only 10% Fewer Breast Cancer Deaths With Routine Mammograms
Sept. 22, 2010 - Routine mammograms reduce breast cancer deaths by only 10% -- far less than the 15% to 23% estimated for the U.S., a new study shows.
The findings call into question one of the cornerstones of U.S. health care: that all women should get regular mammograms once they reach a certain age. The advice is so entrenched that it often is used as a measure of health care quality.
The study, performed in Norway, was not a clinical trial that randomly assigned women to get or not get mammograms. But because Norway began breast cancer screening in some parts of the country before others, it was able to look at screened and unscreened women who got breast cancer at the same time -- and to compare each group to matched women in the pre-screening era.
"When we launched the breast cancer screening program in Norway, we expected to reduce breast cancer deaths by 30% in 10 years," Mette Kalager, MD, of Oslo University Hospital, tells WebMD. "But we found only a 10% reduction in death from breast cancer. It's far less than we expected it to be."
Breast cancer deaths did, indeed, go down by 30% in the screened group. But unscreened women had a 20% drop in cancer deaths. This, Kalager says, was largely due to a policy of having all women with breast cancer treated by teams that included radiologists, oncologists, surgeons, nurses, and other professionals working closely together.
Rethinking Routine Mammograms
The findings apply to routine mammograms -- that is, regular mammograms to screen for new breast cancers in women at normal risk. They do not apply to any woman who finds a lump in her breast, or feels that there is anything abnormal about her breast.
Women with previous breast cancer and those with a close relative who had breast cancer before age 65 are at higher risk. Such high-risk women clearly benefit from regular mammograms.
In the U.S., even normal-risk women are strongly urged to undergo regular mammograms. That advice has not changed, but it varies:
- The American Cancer Society recommends annual mammograms for all women beginning at age 40 and continuing as long as a woman is in good health.
- The U.S. Preventive Services Task Force recommends mammograms once every two years for all women from ages 50 to 74.