Diagnostic accuracy of MRI to evaluate tumour response and residual tumour size after neoadjuvant chemotherapy in breast cancer patients

Purpose. To estimate the accuracy of magnetic resonance imaging (MRI) in assessing residual disease in breast cancer patients receiving neoadjuvant chemotherapy (NAC) and to identify the clinicopathological factors that affect the diagnostic accuracy of breast MRI to determine residual tumor size following NAC. Methods. 91 breast cancer patients undergoing NAC (92 breast lesions) were included in the study. Breast MRI was performed at baseline and after completion of NAC. Treatment response was evaluated by MRI and histopathological examination to investigate the ability of MRI to predict tumor response. Residual tumor size was measured on post-treatment MRI and compared with pathology in 89 lesions. Clinicopathological factors were analyzed to compare MRI-pathologic size differences. Results . The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for diagnosing invasive residual disease by using MRI were 75.00, 78.57, 88.89, 57.89, and 76.09%. The Pearson´s correlation coefficient (r) between tumor sizes determined by MRI and pathology was r= 0.648 (p<0.001). The size discrepancy was significantly lower in cancers with initial MRI size ≤5 cm (p=0.050), in cancers with high tumor grade (p<0.001), and in patients with hormonal receptor-negative cancer (p=0.033). Conclusions. MRI is an accurate tool for predicting tumor response after NAC. The accuracy of MRI in estimating residual tumor size varies with the baseline MRI tumor size, the tumor grade and the hormonal receptor status.