Supplemental Screening Breast US in Women with Negative Mammographic Findings: Effect of Routine Axillary Scanning.

Purpose To evaluate the effect of routine axillary scanning when supplemental screening breast ultrasonography (US) is performed in women with negative mammographic findings. Materials and Methods This retrospective review included 12 844 screening breast US examinations performed in 8664 asymptomatic women aged 40 years or older with dense breasts and negative results for cancer at mammography performed between January 2012 and December 2014. Bilateral whole-breast US was performed with a handheld device by one of 10 experienced radiologists. The bilateral axillae were routinely scanned, and representative images were documented in all examinations. The abnormal interpretation rate (AIR), cancer detection rate (CDR), and positive predictive value (PPV) of screening breast US with and without axillary scanning were calculated. The 95% confidence intervals (CIs) were calculated for cancer detection after an abnormal finding at screening US. Results The frequency of positive axillary findings was 3.5 per 1000 (14 of 4009) baseline screening US examinations and 2.2 per 1000 (19 of 8835) subsequent screening US examinations. Of the 33 women with 33 positive axillary findings, 11 had positive breast findings; none were diagnosed with breast cancer. The remaining 22 women showed positive findings only in the axilla. The axillary findings revealed no malignancy at biopsy (n = 12) or during 22-54-month follow-up (n = 21) (95% CI: 0%, 10.6%). Without routine axillary scanning, the AIR of screening US decreased from 15.2% (610 of 4009 examinations) to 15.0% (602 of 4009 examinations) at baseline US and from 8.1% (714 of 8835 examinations) to 7.9% (700 of 8835 examinations) at subsequent US examinations, and the PPV for biopsy performed increased from 6.0% (five of 83 examinations) to 6.4% (five of 78 examinations) at baseline US and from 7.6% (13 of 170 examinations) to 7.9% (13 of 164 examinations) at subsequent US examinations, without a change in the CDR. Conclusion Routine axillary scanning during screening breast US had no effect on additional cancer detection, but rather increased the number of false-positive results. However, the conclusions based on these findings must be tempered by the low rate of positive findings. RSNA, 2017.