News: U/S plus mammography increase detection and false positives

July 1, 2008

Combining mammography with U/S boosts the breast cancer detection rate in women at high risk by almost 30%.

Combining mammography with a single screening ultrasound boosts the breast cancer detection rate in women at high risk for the disease by almost 30%, but also potentially subjects about one in 10 of them to an unnecessary biopsy because of a fourfold increase in false-positive results.

Over a 2-year period, researchers recruited almost 3,000 women with heterogeneously dense breast tissue in at least one quadrant. Adding U/S to mammography increased the diagnostic yield from 7.6 per 1,000 women with mammography alone to 11.8 per 1,000 women. The supplemental yield was 4.2 per 1,000 women screened (95% CI, 1.1–7.2 per 1,000, P=.003). The diagnostic accuracy for mammography was 0.78 (95% CI, 0.67–0.87) and increased to 0.91 (95% CI, 0.84–0.96) when ultrasound was added (P=.003).

The bottom line is that the combined strategy increases detection, particularly of small and node-negative tumors that are traditionally difficult to see on mammography. Unfortunately, it also subjects a number of women to the unnecessary stress, anguish, and cost of a false-positive result. Since most cancers seen only on U/S are in women with more than 50% dense breast tissue, the dual screening strategy may best be reserved for women at increased risk for the disease.

Berg WA, Blume JD, Cormack JB, et al. Combined screening with ultrasound and mammography vs mammography alone in women at elevated risk of breast cancer. JAMA. 2008;299:2151-2163.

Commentary by Leon Speroff, MD,Professor of Obstetrics and Gynecology, Oregon Health and Science University School of Medicine, Portland, OR.

The important question to ask about this study is: Howmany false positives should we “spend” in order to detect additional cases of breast cancer? In the BergWA, et al. trial, the gain was an additional 29%-that isthe percentage of cancers detected by U/S alone. If awomen is at elevated risk for the disease, that’sprobably a reasonable price to pay. These patients areprobably less concerned about a false¯positive readingthan they are about a missed diagnosis of breast CA.