Level of evidence: 3
Several studies have reported instances of breast cancer detected by ultrasound that were missed by mammography, as discussed in one review. In a pilot study of ultrasound as an adjunct to mammography in 149 women with moderately increased risk based on family history, one cancer was detected, based on ultrasound findings. Nine other biopsies of benign lesions were performed. One was based on abnormalities on both mammography and ultrasound, and the remaining eight were based on abnormalities on ultrasound alone. A large study of 2,809 women with dense breast tissue (ACRIN-6666) demonstrated that ultrasound increased the detection rate due to breast cancer screening from 7.6 per 1,000 with mammography alone to 11.8 per 1,000 for combined mammography and ultrasound. However, ultrasound screening increases false-positive rates and appears to have a limited benefit in combination with MRI. In a multicenter study of 171 women (92% of whom were BRCA1/BRCA2 mutation carriers) undergoing simultaneous mammography, MRI, and ultrasound, no cancers were detected by ultrasound alone. Uncertainties about ultrasound include the effect of screening on mortality, the rate and outcome of false-positive results, and access to experienced breast ultrasonographers.
Level of evidence: None assigned
Other screening modalities
A number of other techniques are under active investigation, including tomosynthesis, contrast-enhanced mammography, thermography, and radionuclide scanning. Additional evidence is needed before these techniques can be incorporated into clinical practice.
In the general population, both subcutaneous mastectomy and simple (total) mastectomy have been used for prophylaxis. Only 90% to 95% of breast tissue is removed with subcutaneous mastectomy. In a total or simple mastectomy, removal of the nipple-areolar complex increases the proportion of breast tissue removed compared with subcutaneous mastectomy. However, some breast tissue is usually left behind with both procedures. The risk of breast cancer following either of these procedures has not been well established.
The effectiveness of risk-reducing mastectomy (RRM) in women with BRCA1 or BRCA2 mutations has been evaluated in several studies. In one retrospective cohort study of 214 women considered to be at hereditary risk by virtue of a family history suggesting an autosomal dominant predisposition, three women were diagnosed with breast cancer after bilateral RRM, with a median follow-up of 14 years. As 37.4 cancers were expected, the calculated risk reduction was 92% (95% CI, 76.6-98.3). In a follow-up subset analysis, 176 of the 214 high-risk women in this cohort study underwent mutation analysis of BRCA1 and BRCA2. Mutations were found in 26 women (18 deleterious, eight variants of uncertain significance). None of those women had developed breast cancer after a median follow-up of 13.4 years. Two of the three women diagnosed with breast cancer after RRM were tested, and neither carried a mutation. The calculated risk reduction among mutation carriers was 89.5% to 100% (95% CI, 41.4%-100%), depending on the assumptions made about the expected numbers of cancers among mutation carriers and the status of the untested woman who developed cancer despite mastectomy. The result of this retrospective cohort study has been supported by a prospective analysis of 76 mutation carriers undergoing RRM and followed prospectively for a mean of 2.9 years. No breast cancers were observed in these women, whereas eight were identified in women undergoing regular surveillance (HR for breast cancer after RRM = 0 [95% CI, 0-0.36]).