The ASTOUND interim analysis shows that ultrasound has better incremental [breast cancer] detection than tomosynthesis in mammography-negative dense breasts at a similar [false-positive] recall rate.— Alberto S. Tagliafico, MD, and colleagues
As reported in the Journal of Clinical Oncology by Alberto S. Tagliafico, MD, of the University of Genoa, and colleagues, interim findings in the Italian prospective ASTOUND study indicate that ultrasound is associated with improved incremental detection of breast cancer at screening compared with tomosynthesis in women with mammography-negative dense breasts.1 Nehmat Houssami, MBBS, MPH, PhD, of the University of Sydney, is the corresponding author of the Journal of Clinical Oncology article.
In the study, 3,295 participants from five screening centers in Italy with negative two-dimensional (2D) mammography and dense breasts were enrolled between December 2012 and March 2015. All participants were to undergo tomosynthesis and ultrasound screening after mammography; 64 women declined to undergo tomosynthesis, resulting in inclusion of 3,231 women in the analysis.
Readers were blinded to the sequential adjunct test results. The same radiologist reported the 2D mammography and tomosynthesis images. Ultrasound was then performed by another radiologist who was blinded to the tomosynthesis images but knew that 2D mammography was negative.
Nehmat Houssami, MBBS, MPH, PhD
All women were asymptomatic; median age was 51 years (range = 38–88 years). Outcome measures were the number and rates of cancers detected per 1,000 screens, the number and percentage of false-positive recalls, and the incremental cancer detection rate. The results presented are from a preplanned interim analysis at approximately 3,000 screens. The screen target for the study is 6,000.
Overall, 24 additional breast cancers were detected, including 23 invasive cancers (18 invasive ductal, 4 invasive lobular, and 1 mixed invasive type) and 1 ductal carcinoma in situ. A total of 13 cancers were detected by tomosynthesis (incremental cancer detection rate = 4.0 per 1,000 screens, 95% confidence interval [CI] = 1.8–6.2) vs a total of 23 detected by ultrasound (incremental cancer detection rate = 7.1 per 1,000 screens, 95% CI = 4.2–10.0; P = .006). One cancer (4%) was detected only by tomosynthesis, and 11 tumors (46%) were detected only by ultrasound.
Overall, incremental false-positive recalls occurred for 107 participants (3.33%, 95% CI = 2.72%–3.96%), with 38 (1.18%) having biopsy (needle biopsy, with excisional biopsy also required in two cases). False-positive recall rates for any testing were 1.7% (n = 53) for tomosynthesis and 2.0% (n = 65) for ultrasound (P = .26). False-positive recall rates for biopsy were 0.7% (n = 22) for tomosynthesis and 0.7% (n = 24) for ultrasound (P = .86).
Among false-positive recalls for any testing, tomosynthesis was positive for 11 and negative for 54 of the 65 ultrasound recalls, and ultrasound was negative for 42 of the 53 tomosynthesis recalls. Among false-positive recalls for biopsy, tomosynthesis was positive for 8 and negative for 16 of the 24 ultrasound recalls, and ultrasound was negative for 14 of the 22 tomosynthesis recalls. The positive predictive value for recall leading to biopsy was 13 per 35 screens (37%, 95% CI = 21.3%–55.4%) for tomosynthesis and 23 per 47 screens (48%, 95% CI = 34.1%–63.9%) for ultrasound.
The investigators concluded:
“The Adjunct Screening With Tomosynthesis or Ultrasound in Women With Mammography-Negative Dense Breasts [ASTOUND] interim analysis shows that ultrasound has better incremental [breast cancer] detection than tomosynthesis in mammography-negative dense breasts at a similar [false positive]-recall rate. However, future application of adjunct screening should consider that tomosynthesis detected more than 50% of the additional [breast cancers] in these women and could potentially be the primary screening modality.” ■
Disclosure: The study was supported by the Associazione Italiana per la Ricerca sul Cancro, the University of Genoa, and the National Breast Cancer Foundation Australia. For full disclosures of the study authors, visit www.jco.ascopubs.org.
1. Tagliafico AS, Calabrese M, Mariscotti G, et al: Adjunct screening with tomosynthesis or ultrasound in women with mammography-negative dense breasts: Interim report of a prospective comparative trial. J Clin Oncol. March 9, 2016 (early release online).