A practical approach to manage additional lesions at preoperative breast MRI in patients eligible for breast conserving therapy: results

The aim of this prospective study was to evaluate the efficacy of directives, established to handle additional lesions at preoperative contrast-enhanced magnetic resonance imaging (MRI). Six-hundred-and-ninety consecutive patients with pathology-proven breast cancer planned for BCT based on clinical examination and conventional imaging underwent preoperative breast MRI. The incidence of additional lesions detected at MRI and impact on management were evaluated. Additional findings were pathology-proven or considered benign by follow-up. Findings for which no pathology proof was available prior to surgery, were defined as Unidentified Breast Objects (UBOs). Patients with multicentric or contralateral UBOs underwent BCT as planned with annual follow-up. Multifocal UBOs in the vicinity of the index cancer were excised with wider local margins. Preoperative MRI detected 141 additional lesions in 121 patients (17.5%). Of these lesions, 44.0% were proven malignant. Additional findings classified as UBOs were found in 81 patients (11.7%). None of the UBOs outside the primary tumour region resulted in malignant disease at follow-up after BCT (mean follow-up time: 57.1 months). However, most multifocal UBOs (in the vicinity of the primary) were malignant (77.5%). The strategy to pursue BCT with larger wide-local excisions for multifocal UBOs and to follow-up multicentric and contralateral UBOs with conventional imaging is effective to exclude malignancy at follow-up. After second-look targeted ultrasound has been performed, MRI-guided biopsy of BIRADS-3 multicentric and contralateral additional findings may have limited complementary clinical value.