Shin GW, et al. - Researchers ascertained if background parenchymal enhancement (BPE) of the contralateral breast on preoperative dynamic contrast-enhanced (DCE)-MRI is associated with therapy outcome in ER-positive, HER2-negative, node-negative invasive breast cancer. Participants were two hundred eighty-nine patients with unilateral ER-positive, HER2-negative, node-negative breast cancer larger than 5 mm. In patients with ER-positive, HER2-negative, node-negative invasive breast cancer, contralateral BPE revealed no correlation with survival outcome. The data presented in this work showed a high Ki-67 expression level was correlated with both worse recurrence-free and distant metastasis-free survival.