Mammography and subsequent whole-breast sonography of nonpalpable breast cancers: the importance of radiologic breast density.

OBJECTIVE: Our purpose was to determine the contribution of mammography followed by sonography for the detection of nonpalpable breast cancers in Breast Imaging Reporting and Data System (BI-RADS) density grades 1-4 breasts, in grades 1 and 2 breasts, and in grades 3 and 4 breasts.

MATERIALS AND METHODS: The results of physical, mammographic, and sonographic examinations performed in 4236 patients were reviewed to determine the sensitivities of mammography and sonography for the detection of nonpalpable breast cancers and to calculate the relative risk for detecting nonpalpable breast cancers using sonography in comparison with mammography in density grades 1-4, grades 1 and 2, and grades 3 and 4 breasts. Sonography was performed after mammographic interpretation.

RESULTS: Sensitivities of mammography and subsequent sonography for the detection of nonpalpable breast cancers were 69% and 88% in grades 1-4, 80% and 88% in grades 1 and 2, and 56% and 88% in grades 3 and 4 breasts, respectively. The relative risk for detecting nonpalpable breast cancers using sonography was statistically significantly greater than that for detecting nonpalpable breast cancers using mammography in grades 1-4 (relative risk, 1.29; p = 0.024) and in grades 3 and 4 (relative risk, 1.57; p = 0.013) but not in grades 1 and 2 (relative risk, 1.1; p = 0.445) breasts.

CONCLUSION: Sonography is a useful adjunct after mammography for the detection of nonpalpable breast cancer, particularly in the dense breast.