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MKSAP 18 "Quiz Me!" Question: Answer and Critique

Answer

D: No further testing

Educational Objective

Avoid adjunctive breast cancer screening in a low-risk patient with dense breast tissue.

Critique

This patient should not undergo adjunctive screening. Breast density is an increasingly recognized risk factor for breast cancer. It is categorized by the Breast Imaging Reporting and Data System (BI-RADS) as (a) almost entirely fatty, (b) scattered areas of fibroglandular tissue, (c) heterogeneously dense, or (d) extremely dense. Women with dense breasts should be informed that high breast density is common (present in up to 50% of women) and increases breast cancer risk but not breast cancer–related mortality. Dense breasts also decrease the sensitivity of mammography. However, women with high breast density without additional risk factors may experience more harms than benefits from supplemental breast imaging. Although supplemental screening with ultrasonography or MRI may increase the cancer detection rate, the impact on important clinical outcomes is unknown. Up to 90% of positive results on supplemental ultrasonography and 66% to 97% of positive results on supplemental MRI are false-positive findings, which may result in additional testing or invasive procedures. Despite this, nearly a quarter of state legislatures mandate that patients be notified of breast density findings, and some specifically recommend adjunctive screening with ultrasonography.

Women with dense breasts and other risk factors that impart a lifetime risk for breast cancer of 20% to 25% or higher, as calculated by models largely dependent on family history, should also undergo breast MRI in addition to screening mammography. The use of supplemental breast MRI in women who have less than a 20% lifetime risk for breast cancer is not currently supported by guidelines.

Digital breast tomosynthesis creates a three-dimensional image of the breast. Clinical studies suggest that tomosynthesis may have a sensitivity equal to or exceeding the sensitivity of digital mammography in the detection of breast cancer in women with dense breasts and that tomosynthesis may decrease the recall rate from screening mammography. Despite these promising findings that may improve screening accuracy, there are no randomized trials or long-term follow-up data.

Most major breast cancer screening guidelines promote biennial screening from age 50 to 75 years. No guideline recommends biannual digital mammography for patients whose only risk factor is high breast density.

Key Point

High breast density alone does not necessitate adjunctive breast imaging other than routine screening mammography.

Bibliogrpahy

Melnikow J, Fenton JJ, Whitlock EP, Miglioretti DL, Weyrich MS, Thompson JH, et al. Supplemental screening for breast cancer in women with dense breasts: a systematic review for the U.S. Preventive Services Task Force. Ann Intern Med. 2016;164:268-78.

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