Mammography Cuts Breast Cancer Deaths by 28%: Study
But experts say women still need risks, benefits spelled out
They evaluated more than 15 million person-years of observation, finding breast cancer deaths occurred in 1,175 of the women invited for a mammogram, and nearly 9,000 of those who weren't invited for screening. "Person-years" is a method used by researchers to take into account the number of people in a study and the amount of time each was in it.
The 28 percent reduction in breast cancer deaths they found means that for every 10,000 women invited to get a mammogram, about 27 deaths from breast cancer could be avoided.
The researchers then estimated the effect of the invitation to get a mammogram among women who actually got one, figuring that about three-quarters followed through. They estimated a 37 percent reduction in breast cancer deaths among women who actually got the exam.
Besides evaluating the effect of the mammograms on breast cancer deaths, "a second aim was to find out how many women need to be invited to mammography screening to prevent one breast cancer death," Vatten said. "And we found that 368 women need to be invited to prevent one death."
Furthermore, 280 women would need to be screened to prevent one breast cancer death, they estimated.
The benefits found in the Norwegian study reflect the findings of other studies, said Robert Smith, director of cancer screening for the American Cancer Society.
Smith, who wasn't involved in the study, said he, too, would describe the benefits found as substantial.
"This provides strong support for the value of a screening program for breast cancer," Smith said. However, the study wasn't designed to assess when mammograms should begin or how often they should be repeated.