Mammograms have only a "modest" impact on reducing breast cancer deaths, according to a study published on September 23 that added to a growing debate on the effectiveness of the routine screening. The research in the New England Journal of Medicine found that a Norwegian screening program resulted in a 10 percent reduction in breast cancer mortality among women between 50 and 69 years.
This figure was "disappointingly small," and below the 15 to 23 percent reduction estimated for many years by US public health officials, said Gilbert Welch, a medical researcher at Dartmouth University, in an editorial accompanying the study.
Moreover, Welch said the 10 percent figure may be an exaggeration because of other outreach efforts to Norwegian women, and said "the relative reduction in mortality due to screening mammography alone could be as low as two percent."
The new study highlighted a rift over the long recommendation for annual screenings.
Welch said that even if the 10 percent figure were accurate, "2,500 women would need to be screened over a 10-year period for one to avoid death from breast cancer," he said.
"What happens to the other 2,499 women who had to undergo screening to achieve this benefit is also relevant. Estimates of harm vary considerably."
Welch added that there are varying degrees of false positive results and treatment that might not be needed for some women.
"But by highlighting that the mortality benefit is modest, the latest findings help confirm that the decision about whether to undergo screening mammography is, in fact, a close call," he wrote. The latest research followed the outcomes of 40,000 women in Norway between 1996 and 2005.