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.