Recommendations from multiple societies differ in terms of breast screening method, age of initiation and frequency of screening, and may be subject to authors’ bias and conflicts of interest. The American College of Physicians (ACP) recently published a guidance statement critically appraising the validity of previously published guidelines for breast cancer screening among average-risk women. The authors conducted a literature search and included the following guidelines for review: US Preventive Services Task Force (USPSTF), American College of Radiology (ACR), American Cancer Society (ACS), American College of Obstetricians and Gynecologists (ACOG), National Comprehensive Cancer Network (NCCN), World Health Organization (WHO), and the newly published 2018 Canadian Task Force on Preventive Healthcare (CTFPHC).
Five authors individually reviewed and scored each guideline for editorial independence, clinical applicability, and evidence supporting each recommendation. Guidelines with the highest score received the most weight for the guidance statement, which included the USPSTF, ACS, and CTFPHC. The ACP Clinical Guidelines Committee worked with ACP members and the public to develop and review the guidance statement.
The ACP guidance statement encourages a shared decision-making model for breast cancer screening with mammography before age 50, specifically citing that the potential harms outweigh the benefits in most women aged 40 to 49 years. This softer recommendation against breast cancer screening in this age group comes on the heels of the 2018 recommendation by the CTFPHC, which does not recommend screening women aged 40-49. For women aged 50-74, the guidance statement recommends offering biennial mammography. In addition, the ACP now recommends against the use of a clinical breast exam for screening average-risk women of all ages.
The seven guidelines all considered the same trials and data when making recommendations, yet reached different conclusions. For example, the USPSTF found no reduction in breast cancer-related mortality for women aged 39-49, while the ACS found a relative risk reduction of 0.85 (95% CI 0.75-0.96) with an estimated number needed to screen over 15 years of 2,463. For women who begin annual mammography at age 40, the estimated cumulative false positive result over a 10-year timeframe is estimated to be 61% (95% CI 59%-63%). No randomized trials have compared annual versus biennial mammography; however, observational data have found no difference in breast cancer-related mortality when comparing annual to biennial screening. In modeling studies, annual mammography increases the rate of false positive (845 per 1,000 screened) and unnecessary biopsies (82 per 1,000 women screened) compared to biennial mammography. The evidence for screening mammography after age 69 is also limited, and the statement recommends against screening women with a life expectancy of 10 years or less or after 75 years of age.
Engaging in a model of shared decision-making for breast cancer screening represents a formidable challenge for clinicians, especially when formal guidelines conflict. These guidance statements provide some clarity for a discussion of the benefits and harms of breast cancer screening that might otherwise be characterized by shades of grey.
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