Study Finds Mammograms Offer Modest Benefit
Published September 23, 2010
LOS ANGELES – Mammograms don't help women over 50 as much as has been believed, new research suggests.
Only a third of the reduced risk of death credited to breast cancer screening is actually deserved — the rest is due to better treatment and greater awareness of the disease, a large study in Norway found.
The research, published in Thursday's New England Journal of Medicine, is the latest to show that the benefits of mammography are limited.
"It's not the great lifesaver that people think it is. It's not a magic bullet," said Georgetown University researcher Dr. Jeanne Mandelblatt who was not involved in the study.
Mandelblatt headed six teams that helped shape the new mammogram guidelines issued last year by an influential government task force. The U.S. Preventive Services Task Force concluded that women at average risk for breast cancer don't need mammograms in their 40s and should get one just every two years starting at 50.
The World Health Organization estimates that mammograms reduce the breast cancer death rate by 25 percent in women over 50. Other groups put the figure at 15 to 23 percent.
The latest study found that while mammograms cut the risk of dying, the benefit was disappointingly low. Women who were screened had a 10 percent lower risk of death from breast cancer, but only a third of that reduction was due to screening itself.
Some 2,500 women would have to be regularly screened over 10 years to save one life from breast cancer, Dr. H. Gilbert Welch of Dartmouth Medical School noted in an accompanying editorial.
In the study, scientists were able to tease out the benefits of mammography by studying Norway's breast cancer screening program, which began as a pilot in 1996 and later expanded to the entire country. As part of the national screening program, teams of doctors were set up in every county to treat any breast cancer cases that did occur, whether they were found by mammograms or other ways.
Among women in the screening group, the breast cancer death rate declined by 7.2 deaths per 100,000 people compared with women in the decade before the screening program started. The death rate in the non-screening group fell by 4.8 deaths per 100,000 people compared with its historical counterpart.
That means that mammography reduced mortality by only 2.4 deaths per 100,000 people — a third of the total risk of death.