It was not possible to "tease out" the specific benefit of screening women in their 40s, one area of debate, he noted. But other reviews suggest that "although the benefit is smaller, there is still a mortality reduction with screening women in their 40s," Duffy said.
At the end of the study, the investigators found 30 percent fewer breast cancer deaths overall in the group invited to screening compared to those not screened.
There was also a substantial absolute reduction in cancer deaths. At 29 years of follow-up, 34 to 42 years of life were saved for each 1,000 women screened for seven years, and one breast cancer death prevented for every 414 to 519 women. Had the screening continued another 10 years with the same benefits, only 300 screenings would be needed to save one life, the study reported.
In addition, for every 1,000 women screened every two years from ages 40 to 69, about eight to 11 deaths from breast cancer would be prevented, according to the study authors.
Duffy said he does not expect the study results to put to rest the mammography debate.
"There will always be skeptics, who argue that the benefits of screening are too small to justify its financial and human costs," Duffy said. "They have tended to argue this on the basis of deaths prevented during 10 years of screening. Our results show that this argument is invalid, since the majority of the mortality benefit occurs more than 10 years after starting screening."
He and his colleagues noted that the drawbacks of mammography include the risk of radiation exposure and over-diagnosis. However, they wrote that the radiation dose in this trial was much smaller than most modern procedures since it was single-view mammography and over-diagnosis occurred in only a "small fraction" of the cases.
The findings are similar to those from previous studies, said Dr. Virginia Moyer, head
All rights reserved