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 .
The National Comprehensive Cancer Network recommends routine mammography for women starting at age 40 and the American Cancer Society recommends starting at age 45 [3-4].
Weighing the benefits and risks, the U.S. Preventive Services Task Force does not recommend routine mammography for all women 40 to 49 .
Instead, the Task Force, as well as the American College of Physicians, recommends that women 40 to 49 discuss the pros and cons of mammography with their health care providers. Then, together, women and their providers make informed decisions about when to start mammography screening [5-6]. Similarly, the American Cancer Society recommends informed decision-making for women ages 40 to 44 .
Learn more about mammography in women 40 to 49.
Learn about the debate over mammography for women of any age.
Read Komen’s recent press release on this topic.
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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