Adding Ultrasound Best for Cancer Detection in Dense Breasts

March 18, 2016

Ultrasound proved better than tomosynthesis at finding breast cancer in women with dense breasts where mammography had not detected any cancer.

Ultrasound proved better than tomosynthesis at detecting breast cancer in women with dense breasts where mammography had not detected any cancer. Both modalities had a comparable false-positive rate. Tomosynthesis, however, may be better than mammography in these patients as a primary screening tool, according to the interim results of the ASTOUND (Adjunct Screening With Tomosynthesis or Ultrasound in Women With Mammography-Negative Dense Breasts) trial. These results were published in the Journal of Clinical Oncology.

Among 3,231 women with dense breasts where mammography had not detected any cancer, 24 addition cases of breast cancer were detected: 23 were invasive and 1 was non-invasive. Thirteen of the cases were detected with tomosynthesis compared to 23 detected by ultrasound imaging (P = .006). The incremental cancer detection rate (CDR) was 7.1 per 1,000 screens using ultrasound compared with an incremental CDR rate of 4 per 1,000 screens with tomosynthesis. The false-positive rate was 3.33% (107 participants), including 53 false-positive cases with tomosynthesis and 65 cases with ultrasound (P = .26).

Dense breast tissue is a risk factor for breast cancer and can prohibit the detection of a breast tumor using mammography-a negative mammogram in a woman with dense breasts does not rule out that no cancer is present.

“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,” wrote Nehmat Houssami, MBBS, MPH, PhD, of the University of Sydney, and colleagues.

Most of the cancers detected by ultrasound but not by tomosynthesis were masses, while the only cancer detected by tomosynthesis but not by ultrasound was an architectural distortion.

Ultrasound is time and resource intensive, the authors noted. “Therefore, a comprehensive cost-effectiveness evaluation is needed to define the comparative costs of these adjunct screening methods, factoring in screen-detection metrics and the potential for tomosynthesis to eliminate the 2D-mammography acquisition, which would significantly impact resource utilization.”

In an accompanying editorial, Wendie Berg, MD, PhD, of the University of Pittsburgh Cancer Institute in Pennsylvania, highlighted that some of the barriers to implementing screening are high rates of false positives, clinicians trained for screening, and out-of-pocket cost for patients. Berg pointed out that the false-positive rates “were acceptably low” in the ASTOUND trial-2% for recalls and 0.7% for biopsies.

“Preliminary results from ASTOUND are extremely important in helping to inform personalized screening choices for women with dense breasts,” Berg wrote.

Berg suggested that based on the ASTOUND trial results, “Ultrasound would seem the clear choice compared with tomosynthesis” yet because of barriers for implementation of ultrasound, “supplemental ultrasound after tomosynthesis would still be reasonable, although further study is warranted,” she concluded.