Added cancer yield of MRI in screening the contralateral breast of women recently diagnosed with breast cancer: results from the International Breast Magnetic Resonance Consortium (IBMC) trial.

Objective: To estimate the added cancer yield of magnetic resonance imaging (MRI) over mammography in the contralateral breast of patients with a recent diagnosis of breast cancer.

Methods: We conducted a prospective, international study of mammography and MRI in women with a recent diagnosis of unilateral breast cancer. Each subject received a mammogram, clinical breast exam (CBE), and MRI of the unaffected breast within a 90 day time period. Definitive diagnosis of suspicious findings was determined through biopsy and central pathology review.

Results: Of the 103 eligible women included in study analyses, MRI detected 4 cancers in the contralateral breast while mammography detected none. MRI resulted in 12% (95% CI, 6%-20%) of women recommended for biopsy and 10% of women undergoing additional biopsy. The added cancer yield of MRI was 4% (95% CI, 1%-10%) and the positive predictive value of an abnormal MRI was 33% (95% CI, 10%-65%). Forty percent (4/10) of the biopsies performed based on the MRI recommendation were positive for malignancy.

Conclusion: In women with a recent breast cancer diagnosis, approximately 4% will have an otherwise occult invasive breast cancer detected in the opposite breast by MRI alone.