The Yield of Pre-operative Breast MRI in Patients According to Breast Tissue Density

To determine the yield of pre-operative breast MRI according to breast tissue density.

We performed a retrospective review of 665 consecutive patients who underwent breast MRI in 2012 for pre-operative staging of biopsy-proven breast cancer, 582 of whom had digital mammograms available within 6 months of the MRI were evaluated for breast tissue density and additional lesions seen on breast MRI not identified on mammography. Lesions that could change surgical management if positive were confirmed by percutaneous biopsy.

MRI identified additional lesions changing surgical management in 19 of 61 patients (31%) with fat density, 94/269 (35%) with scattered fibroglandular parenchyma, 89/210 (42%) with heterogeneously dense breasts, and 26/42 (62%) with dense breasts. There was a significant difference between breast density and number of additional findings on MRI (p<0.0001). Patients with dense breasts were 5.1x more likely to have additional findings on MRI in comparison to patients with fat density breasts (95% CI 2.2-12.1, p=0.0001).

Patients with dense breasts are more likely to have additional findings on pre-operative breast MRI in comparison to patients with fat tissue density breasts; if selective use of pre-operative MRI is necessary, patients with dense breast tissue density seem to show the maximal benefit.

• Preoperative MRI detects many additional lesions not seen on mammography. • Increased breast density correlates with more findings on preoperative breast MRI (p<0.0001). • Extremely dense breasts are more likely to have additional findings on MRI. • Increased breast density is associated with more MRI findings that changed management.