Diagnostic Performance of Magnetic Resonance Imaging for Assessing Tumor Response in Patients With HER2-Negative Breast Cancer Receiving Neoadjuvant Chemotherapy is Associated With Molecular Biomarker Profile

The influence of hormone receptors (HRs) and the Ki-67 proliferation marker in the accuracy of measuring tumor size by magnetic resonance imaging (MRI) after chemotherapy was investigated in 54 patients with HER2-negative (HER2(-)) breast cancer. The accuracy was higher in HR-negative (HR-) tumors than in HR-positive (HR+) tumors and was also higher in tumors with >= 40% Ki-67 staining than in those with < 40% Ki-67 staining, suggesting that the accuracy of MRI is better in more aggressive phenotypes. Background: This study aimed to evaluate the influence of hormone receptor (HR) and Ki-67 proliferation markers in predicting the accuracy of magnetic resonance imaging (MRI) for measuring residual tumor size in patients with HER2-negative (HER2(-)) breast cancer receiving neoadjuvant chemotherapy (NAC). Patients and Methods: Fifty-four women were studied. Patients received AC (doxorubicin (Adriamycin)/cyclophosphamide) and/or taxane-based regimens. The accuracy of MR-determined clinical complete response (CCR) was compared to pathological complete response (pCR). The size of detectable residual tumor on MRI was correlated with pathologically diagnosed tumor size using the Pearson correlation. Results: MRI correctly diagnosed 16 of the 17 cases of pCR. There were 8 false-negative diagnoses: 7 HR+ and 1 HR-. The overall sensitivity, specificity, and accuracy of MRI were 78%, 94%, and 83%, respectively. The positive predictive value was 97% and the negative predictive value was 67%. For MRI vs. pathologically determined tumor size correlation, HR- cancers showed a higher correlation (R = 0.79) than did HR+ cancers (R = 0.58). A worse MRI/pathology size discrepancy was found in HR+ cancer than in HR- cancer (1.6 +/- 2.8 cm vs. 0.56 +/- 0.9 cm; P = .05). Tumors with low Ki-67 proliferation (< 40%) showed a larger size discrepancy than did those with high Ki-67 proliferation (>= 40%) (1.2 +/- 2.0 cm vs. 0.4 +/- 0.8 cm; P = .05). Conclusions: The results showed that the diagnostic performance of MRI for patients with breast cancer undergoing NAC is associated with a molecular biomarker profile. Among HER2(-)tumors, the accuracy of MRI was worse in HR+ cancers than in HR(-)cancers and was also worse in low-proliferation tumors than in high-proliferation tumors. These findings may help in surgical planning.