Is staging breast magnetic resonance imaging for invasive lobular carcinoma worthwhile?

Abstract Background Invasive lobular carcinoma (ILC) is challenging to stage accurately using mammography (MG) and ultrasound (US) with undiagnosed ipsilateral and contralateral cancer resulting in poor patient outcomes including return to surgery. Our institution employs routine staging breast MRI in ILC for this reason. However, increased time for further imaging/biopsies contributes to patient anxiety and potentially delays definite management. We aimed to quantify the frequency of staging MRI‐detected additional lesions requiring biopsy or follow‐up, the added cancer detection rate and MRI prompted change in surgical management. Methods An observational study on staging breast MRI for newly diagnosed ILC at a tertiary Western Australian hospital from January 2019 to August 2022. Standardized 3T MRI protocol was performed, double read by unblinded fellowship‐trained radiologists. Histopathology from biopsy, surgery, or first annual surveillance was the reference standard for additional MRI‐detected lesions. Results One hundred ten MRI studies demonstrated 49 (45%) patients had at least one additional clinically significant MRI‐detected lesion. Thirty‐one patients had an additional ipsilateral lesion detected, of which 18 (58%) proved malignant; 14 (45%) multifocal and 4 (13%) multicentric ILC. Additional work‐up of MRI‐detected lesions averaged a 9‐day delay to definitive surgery compared to patients with a negative or definitively benign MRI. MRI changed surgical planning in 11 of 110 cases from breast conservation surgery (BCS) to mastectomy and there were two contralateral cancers diagnosed. BCS reoperation rate was 11%. Conclusion Staging MRI for ILC identifies clinically significant lesions in nearly half of patients, predominantly ipsilateral multifocal disease, without significant delay to definitive surgery.