USPSTF Updates Screening Mammography Guidance for Average-Risk Women

January 11, 2016

USPSTF Updates Screening Mammography Guidance for Average-Risk Women

  1. Andrew M. Kaunitz, MD

Although largely unchanged from 2009, recommendations address tomosynthesis and adjunctive imaging for women with radiologically dense breast tissue.

  1. Andrew M. Kaunitz, MD

In 2009, the U.S. Preventive Services Task Force (USPSTF) recommended that biennial mammography screening in average-risk women begin at age 50 (NEJM JW Womens Health Dec 2009 and Ann Intern Med 2009; 151:716). Now, based on reviews and modelling studies, the USPSTF has updated and clarified this guidance, with particular attention to individualized screening for women in their 40s, tomosynthesis, and supplemental evaluation for women with radiologically dense breasts.

The new guidance does not apply to women at substantially higher-than-average risk for breast cancer, including those with prior breast cancer or biopsy-confirmed high-risk lesions (e.g., atypical hyperplasia), certain genetic conditions (e.g., BRCA1 or BRCA2 mutation), or histories of chest irradiation (e.g., for Hodgkin lymphoma).

Key statements are as follows:

  • Biennial screening is recommended for women aged 50 to 74 (B recommendation; definitions of USPSTF grades are available online at http://www.uspreventiveservicestaskforce.org/Page/Name/grade-definitions).

  • Initiation of screening before age 50 should be individualized depending on patient preferences (C recommendation).

  • For women aged ≥75, current evidence is insufficient to assess benefits and harms of screening (I statement).

  • Current evidence is insufficient to assess the benefits and harms of adding tomosynthesis to conventional screening mammography (I statement).

  • For women with radiologically dense breasts, current evidence is insufficient to assess the benefits and harms of adjunctive ultrasound, magnetic resonance imaging (MRI), or tomosynthesis (I statement).

In recommending that screening begin at age 50 in average-risk women, the 2009 guidelines generated controversy. The current guidance clarifies that repetitive screening of women through 10 years reduces breast cancer deaths by 4 (aged 40–49), 8 (aged 50–59), and 21 (aged 60-69) per 10,000 women. The term “overdiagnosis” refers to detection and treatment of invasive and noninvasive (usually ductal carcinoma in situ) lesions that would have gone undetected without screening and would not have caused health problems. The USPSTF acknowledges that, while overdiagnosis represents the principal harm from screening, estimating overdiagnosis rates is challenging (best estimates range from 1 in 5 to 1 in 8 breast cancers diagnosed in screened women). False-positive results, which lead to unnecessary additional imaging and biopsies, represent an additional harm of screening mammography.

The rationale for recommending that average-risk women begin screening at age 50 is based on the relatively smaller benefits and greater harms incurred when younger women are screened; however, in noting that most of the screening benefits for women in their 40s are realized starting at age 45, the USPSTF guidance opens the door to average-risk women to begin screening at that age (congruent with the recently updated American Cancer Society recommendations [NEJM JW Womens Health Nov 2015; multiple citations]). Also, women with a first-degree relative with breast cancer may want to initiate screening at age 40.

Regarding screening frequency, annual screening generates minimal, if any, benefit while increasing the potential for harm; thus, for most women, biennial screening provides the best benefit–harm balance.

Tomosynthesis, which can be performed along with conventional digital screening mammography, is a technique that produces multiplanar images of the breast. Tomosynthesis seems to diminish the need for follow-up imaging while also increasing cancer detection rates. However, whether these additional cancers represent overdiagnosis remains unknown. Furthermore, tomosynthesis can expose women to about twice the radiation as conventional digital screening.

Twenty-four states currently mandate that patients with dense breasts identified at screening be notified. Although increased breast density is a common independent risk factor for breast cancer, the degree of radiographic density can vary substantially from one screen to the next in the same woman. Evidence for or against adjunctive imaging is very limited in women found to have dense breasts in an otherwise negative mammogram and suggests that ultrasonography and MRI (as well as tomosynthesis) can detect additional breast cancers while also generating more false-positive results. Thus, the USPSTF does not recommend specific screening strategies for women with dense breasts.

Comment

Although I plan to continue recommending screening based on USPSTF guidance, I will also continue to support the preferences of my patients who prefer to initiate screening before age 50, to undergo screening annually, and to continue screening after age 74. Women and clinicians alike may find the USPSTF's Summary for Patients (Ann Intern Med 2016 Jan 12; [e-pub]) to be helpful when navigating this territory.

Editor Disclosures at Time of Publication

  • Disclosures for Andrew M. Kaunitz, MD at time of publication Consultant / Advisory board Actavis plc; Bayer AG; Merck Royalties UpToDate Grant / Research support Therapeutics MD; Bayer; Agile; NIH Editorial boards Contraception; Menopause; Contraceptive Technology Update; OBG Management; Medscape OB/GYN & Women’s Health Leadership positions in professional societies North American Menopause Society (Treasurer)

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