Addition of ultrasound to mammography in the case of dense breast tissue: systematic review and meta-analysis

Abstract

Background: Mammography is less effective in detecting cancer in dense than in fatty breasts.

Methods: We undertook a systematic search in PubMed to identify studies on women with dense breasts who underwent screening with mammography supplemented with ultrasound. A meta-analysis was undertaken on the proportion of cancers detected only by ultrasound, out of all screen-detected cancers, and the proportion of women with negative mammography who were referred for assessment following ultrasound screening.

Results: Twenty-nine studies satisfied our inclusion criteria. The proportion of total cancers detected only by ultrasound was 0.29 (95% CI: 0.27-0.31), consistent with an approximately 40% increase in the detection of cancers compared to mammography. In the studied populations, this translated into an additional 3.8 (95% CI: 3.4-4.2) screen-detected cases per 1000 mammography-negative women. About 13% (32/248) of cancers were in situ from 17 studies with information on this subgroup. Ultrasound approximately doubled the referral for assessment in three studies with these data.

Conclusions: Studies have consistently shown an increased detection of breast cancer by supplementary ultrasound screening. An inclusion of supplementary ultrasound into routine screening will need to consider the availability of ultrasound and diagnostic assessment capacities.

Fig. 1

PRISMA flow diagram of study selection. Baseline search undertaken on 29 June 2016. Update search undertaken on 26 July 2017. ^a Reference lists of reviews and similar publications were examined for any additional studies reporting primary data. The latter studies were included in the counts of articles assessed for eligibility, and, if they satisfied the inclusion criteria, they were included in the meta-analysis. ^b This number may have included duplicate records compared to the original search. No new studies reporting primary data were identified through reviews and similar secondary publications in the updated search, suggesting that the pool of the relevant studies had been exhausted

Fig. 2

Additional detection of breast cancer cases with ultrasound in mammography negative women, compared to the detection with stand-alone mammography (based on 12 studies reporting detection by both screening modalities). BI-RADS 2 density: breasts with scattered areas of fibroglandular density (sometimes defined as 25–50% fibroglandular tissue). BI-RADS 3 density: breasts with heterogeneously dense tissue (50–75%). BI-RADS 4 density: breasts with extremely dense breast tissue (>75%). CI confidence interval, M mammography, US ultrasound (a) Additional detection, overall results. (b) Additional detection, by definition of breast density. (c) Additional detection, by year of study. (d) Additional detection, by whether the study focused on women with additional risk factors

Fig. 3

Funnel plot of the percentage of cancers detected by ultrasound against the total number of cancers detected (based on 12 studies reporting detection by both screening modalities)

Fig. 4

Extra detection of cases of breast cancer per 1000 women with negative mammography (based on 23 studies reporting detection in mammographically negative women). CI confidence interval