Adjunct Screening With Tomosynthesis or Ultrasound in Women With Mammography-Negative Dense Breasts: Interim Report of a Prospective Comparative Trial

PURPOSE: Debate on adjunct screening in women with dense breasts has followed legislation requiring that women be informed about their mammographic density and related adjunct imaging. Ultrasound or tomosynthesis can detect breast cancer (BC) in mammography-negative dense breasts, but these modalities have not been directly compared in prospective trials. We conducted a trial of adjunct screening to compare, within the same participants, incremental BC detection by tomosynthesis and ultrasound in mammography-negative dense breasts. PATIENTS AND METHODS: Adjunct Screening With Tomosynthesis or Ultrasound in Women With Mammography-Negative Dense Breasts is a prospective multicenter study recruiting asymptomatic women with mammography-negative screens and dense breasts. Eligible women had tomosynthesis and physician-performed ultrasound with independent interpretation of adjunct imaging. Outcome measures included cancer detection rate (CDR), number of false-positive (FP) recalls, and incremental CDR for each modality; these were compared using McNemar's test for paired binary data in a preplanned interim analysis. RESULTS: Among 3,231 mammography-negative screening participants (median age, 51 years; interquartile range, 44 to 78 years) with dense breasts, 24 additional BCs were detected (23 invasive): 13 tomosynthesis-detected BCs (incremental CDR, 4.0 per 1,000 screens; 95% CI, 1.8 to 6.2) versus 23 ultrasound-detected BCs (incremental CDR, 7.1 per 1,000 screens; 95% CI, 4.2 to 10.0), P = .006. Incremental FP recall occurred in 107 participants (3.33%; 95% CI, 2.72% to 3.96%). FP recall (any testing) did not differ between tomosynthesis (FP = 53) and ultrasound (FP = 65), P = .26; FP recall (biopsy) also did not differ between tomosynthesis (FP = 22) and ultrasound (FP = 24), P = .86. CONCLUSION: The Adjunct Screening With Tomosynthesis or Ultrasound in Women With Mammography-Negative Dense Breasts' interim analysis shows that ultrasound has better incremental BC detection than tomosynthesis in mammography-negative dense breasts at a similar FP-recall rate. However, future application of adjunct screening should consider that tomosynthesis detected more than 50% of the additional BCs in these women and could potentially be the primary screening modality.