Factors influencing performance of MRI in newly diagnosed breast cancer patients

Abstract

604 Background: There is wide variation in the use of breast MRI to screen the contralateral breast in patients recently diagnosed with unilateral breast cancer. Some centers routinely scan all patients with a recent diagnosis of breast cancer while others restrict breast MRI to patients with dense breast tissue, patients who are pre-menopausal, or patients with infiltrating lobular carcinoma. This international study evaluated performance measures of MRI by mammographic density, menopausal status and type of index cancer. Methods: 969 women from 21 sites with a recent diagnosis of unilateral breast cancer and a negative mammogram and CBE of the contralateral breast underwent breast MRI. Presence of breast cancer in the contralateral breast was determined by cancer positive breast biopsy within 12 months after study entry. Performance measures of breast MRI (cancer yield, sensitivity, specificity, negative predictive value, positive predictive value, biopsy rate) were compared between participant subsets defined by mammographic density (fatty vs dense), menopausal status (pre/peri menopausal vs post menopausal) and type of index cancer (invasive vs in situ and lobular vs non-lobular). Results: Performance measures of breast MRI were not influenced by breast density or index cancer histology. Cancer yield of MRI in dense breast women was 3% in both fatty and dense breasted women. Although cancer yield and sensitivity of MRI did not vary based on menopausal status, specificity was significantly higher among post-menopausal women in comparison to pre- or peri-menopausal women (p-value=0.002) as was positive biopsy rate (p-value 0.009). Conclusions: Performance of MRI in screening the contralateral breast in the newly diagnosed breast cancer patient is not influenced by breast density or index cancer histology. Specificity and positive biopsy rate are higher in post-menopausal women, which may be related to hormonal influences on breast tissue enhancement. [Table: see text]