Magnetic resonance imaging patterns of tumor regression in breast cancer patients after neo-adjuvant chemotherapy, and an analysis of the influencing factors.

The objective of this study was to analyze the patterns of breast tumor shrinkage in patients after neo-adjuvant chemotherapy (NAC) based on magnetic resonance imaging (MRI), and to evaluate the influential factors. Preoperative breast dynamic contrast-enhanced MRI was performed on 88 patients before NAC, every 2 weeks during their chemotherapy treatment, and the week before their surgery. The MRI enhancement pattern of the primary tumors was classified into one of four categories based on BI-RADS-MRI: type I (postcontrast mass image), II (multiple small masses image), III (postcontrast mass image with peripheral non-mass enhancement image), and IV (nonmass enhancement image). Multivariate regression and χ2 test analyses were employed to establish significant associations. Two kinds of tumor regression patterns were observed: concentric shrinkage was observed in 39 lesions of 88 patients (44.3%), and nests or dendritic shrinkage was observed for the other 49 lesions (55.7%). ER+/HER2-, HER2+, and type I lesions were observed in 23 (62.2%), 21 (63.6%), and 29 (60.0%) patients, respectively, out of 49 nest or dendritic shrinkage pattern lesions. Triple negative breast cancer lesions, and type II, III, and IV lesions were observed in 13 (72.2%), 9 (81.8%), 10 (62.5%), and 10 (76.9%) patients, respectively, out of 39 lesions with a concentric shrinkage pattern. Molecular subtypes (χ2 =7.171, P<.05) and the MRI schedule of enhancement (χ2 =11.244, P<.05) were significantly associated with the tumor regression patterns. Multivariate analysis showed molecular subtypes (P<.05) and MRI pattern enhancement (P<.05) were significant predictive factors. Molecular subtypes and the MRI enhancement patterns of the primary tumors were significant predictive factors for tumor regression patterns of breast cancer after NAC.