Clinical significance of new suspicious enhancement on breast MRI during neoadjuvant chemotherapy

The goal of this study was to evaluate outcomes of new suspicious enhancement in women undergoing breast MRI during neoadjuvant chemotherapy (NAC).

This retrospective review evaluated patients with breast cancer who underwent NAC with breast MRI performed from 2012 to 2022. Patients were included for further evaluation if an MRI during NAC recommended additional workup or biopsy of any new suspicious enhancing lesion separate from the index tumor. Medical records, subsequent imaging studies, and pathology reports were reviewed in eligible patients to identify lesion characteristics and outcomes of further workup.

A total of 425 patients had pre- and post-treatment MRI. After exclusions, final study population included 14/425 (3.3 %) patients with new suspicious findings after initiation of NAC, none (0/14, 0 %) of which were shown to represent malignancy on biopsy, surgery, or follow-up. Imaging manifestations included non-mass enhancement (5/14, 35.7 %), enhancing foci (5/14, 35.7 %), and masses (4/14, 28.6 %), with the new finding contralateral to the malignancy in 10/14 (71.4 %) and ipsilateral in 4/14 (28.6 %). Most patients (11/14; 78.6 %) demonstrated an imaging response to NAC. Of 11 patients with pathology, stromal fibrosis and fibrocystic change were described most commonly, in 8/11 (72.7 %) and 5/11 (45.5 %) respectively. Inflammatory cysts were present in 8/14 patients (57.1 %).

New enhancing lesions on breast MRI during NAC, particularly in setting of treatment response, are unlikely to indicate malignancy. This data corroborates other contemporaneous studies investigating this topic. Radiologists can incorporate this mounting evidence to help limit unnecessary workups.