This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.
Introduction: For women 40-49, mammography screening saves lives, but the benefits are less than for older women.
The U.S. Preventive Services Task Force meta-analysis of 8 randomized controlled trials found mammography modestly reduced the risk of breast cancer mortality (death) in women 40-49 .
The American College of Physicians reviewed 117 studies and found mammography reduced breast cancer mortality in women 40-49, but the risk of false positive results was high .
The National Comprehensive Cancer Network recommends routine mammography for women starting at age 40 . The American Cancer Society recommends starting at age 45 .
Weighing the benefits and risks, the U.S. Preventive Services Task Force does not recommend routine mammography for all women 40-49 .
Instead, the Task Force, as well as the American College of Physicians, recommends women 40-49 discuss the pros and cons of mammography with their health care providers. Then, together, make informed decisions about when to start mammography screening and how often to screen [5-6].
Similarly, the American Cancer Society recommends informed decision-making for women ages 40-44 .
Learn more about mammography in women 40-49.
Learn about weighing the benefits and risks of mammography.
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 
age less than 50
*The combined relative risk for the 3 studies with good methodology was 0.87 (0.73-1.03).
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