Clinical findings and outcomes of MRI staging of breast cancer in a diverse population

Background The performance of magnetic resonance imaging (MRI), the effect of patient factors, and resulting surgical management in underserved and ethnically diverse breast cancer (BC) patient populations have been understudied. Methods We retrospectively analyzed the data of 1116 consecutive patients who were newly diagnosed with in situ or invasive BC with preoperative staging MRI. Non-index lesions (NILs) were defined as abnormal MRI findings with BI-RADS score of 4 or 5 in breast or axillary nodes not previously detected by conventional imaging. Occult cancers (OCs) were NILs found to be malignant by biopsy or surgery. Logistic regression was used to examine associations between probabilities of NILs or OCs and patient characteristics. Results Staging MRI detected NILs and OCs in 24% and 7.5% of patients, respectively. Of 1116 patients, 271 (24%) had 327 NILs, and 84 (7.5%) had 87 OCs. Follow-up information was available for 306 NILs. Ipsilateral breast NILs ( n = 124) were seen in 115 patients (10.3%), with OCs ( n = 51) seen in 48 patients (4.4%). Contralateral breast NILs ( n = 134) were seen in 118 (10.6%) patients, with OCs ( n = 20) seen in 20 patients (1.8%). Laterality ( p < 0.001) and disease stage ( p = 0.018) were associated with probability of OC. Patients without BRCA mutations had a significantly higher probability of having NILs ( p = 0.003) but not OCs. Conclusions Our study provides useful estimates of the rates of NILs and OCs anticipated in a younger, uninsured, ethnically diverse population. Prospective trials and larger pooled retrospective analyses are needed to define the long-term impacts of MRI staging after a BC diagnosis.