Clinical Review

Breast density and optimal screening for breast cancer

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Ultrasonography supplements mammography

Mammography supplemented with ultrasonography (US) has been studied as a “Goldilocks” or best-fit solution for the screening of women with dense breasts, as detection of invasive cancers is improved with the 2 modalities over mammography alone, and US is less invasive, better tolerated, and lower in cost than the more sensitive MRI.

In women with dense breasts, US has been found to improve cancer detection over mammography alone, and early results suggest a larger cancer detection benefit from US than from 3D mammography, although research is ongoing.20 Adding US reduces the interval cancer rate in women with dense breasts to less than 10% of all cancers found—similar to results for women with fatty breasts.17,21,22

US can be performed by a trained technologist or a physician using a small transducer, which usually provides diagnostic images (so that most callbacks would be for a true finding), or a larger transducer and an automated system can be used to create more than a thousand images for radiologist review.23,24 Use of a hybrid system, a small transducer with an automated arm, has been validated as well.25 Screening US is not available universally, and with all these approaches optimal performance requires trained personnel. Supplemental screening US usually is covered by insurance but is nearly always subject to a deductible/copay.

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Educate patients about dense breasts and cancer risk

Reducing false-positives, callbacks, and additional testing

Mammography carries a risk of false-positives. On average, 11% to 12% of women are called back for additional testing after a screening mammogram, and in more than 95% of women brought back for extra testing, no cancer is found.26 Women with dense breasts are more likely than those with less dense breasts to be called back.27 US and MRI improve cancer detection and therefore yield additional positive, but also false-positive, findings. Notably, callbacks decrease after the first round of screening with any modality or combination of tests, as long as prior examinations are available for comparison.

One advantage of 3D over 2D mammography is a decrease in extra testing for areas of asymmetry, which are often recognizable on 3D mammography as representing normal superimposed tissue.28–30 Architectural distortion, which is better seen on 3D mammography and usually represents either cancer or a benign radial scar, can lead to false-positive biopsies, although the average biopsy rate is no higher for 3D than for 2D alone.31 Typically, the 3D and 2D examinations are performed together (slightly more than doubling the radiation dose), or synthetic 2D images can be created from the 3D slices (resulting in a total radiation dose almost the same as standard 2D alone).

Most additional cancers seen on 3D mammography or US are lower-grade invasive cancers with good prognoses. Some aggressive high-grade breast cancers go undetected even when mammography is supplemented with US, either because they are too small to be seen or because they resemble common benign masses and may not be recognized. MRI is particularly effective in depicting high-grade cancers, even small ones.

The TABLE summarizes the relative rates of cancer detection and additional testing by various breast screening tests or combinations of tests. Neither clinical breast examination by a physician or other health care professional nor routine breast self-examination reduces the number of deaths caused by breast cancer. Nevertheless, women should monitor any changes in their breasts and report these changes to their clinician. A new lump, skin or nipple retraction, or a spontaneous clear or bloody nipple discharge merits diagnostic breast imaging even if a recent screening mammogram was normal.

FIGURE 4 is an updated decision support tool that suggests strategies for optimizingcancer detection with widely available screening methods.

Read how to take advantage of today’s technology for breast density screening

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