This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: For women 40 to 49, mammography screening saves lives, but the benefits are less than for older women.
The U.S. Preventive Services Task Force meta-analysis of eight randomized controlled trials found that mammography modestly reduced the risk of breast cancer mortality (death) in women 40 to 49 . An American College of Physicians review of 117 studies found that while mammography reduced breast cancer mortality in women 40 to 49, the risk of false positive results was high .
Weighing the benefits and risks, the U.S. Preventive Services Task Force no longer recommends routine mammography for all women 40 to 49 . Instead, the Task Force, as well as the American College of Physicians, encourages women 40 to 49 to make informed decisions with their health care providers about when to start mammography screening [3-4].
Many health organizations, including the American Cancer Society, feel the modest survival benefit of mammography in women 40 to 49 outweighs the risk of false positive results. They recommend routine screening mammograms for women at average risk beginning at age 40.
Learn more about mammography in women 40 to 49.
Learn about the debate over mammography for women of any age.
Study selection criteria: Large randomized controlled trials and meta-analyses. Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Age at Screening
Relative Risk of Breast Cancer Mortality (Death) in Women Who Got Screening Mammography Versus Women Who Did Not RR (95% CI)
Randomized controlled trials
Age Trial (United Kingdom) 
Canadian National Breast Cancer Screening Study 
Gothenburg Breast Screening Trial 
Kerlikowske et al. 
U.S. Preventive Services Task Force 
Cochrane Collaboration 
*The combined relative risk for the three studies with good methodology was 0.87 (0.73-1.03).
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