Magnetic resonance examination to predict pathological complete response following neoadjuvant chemotherapy: when is it appropriate for HER2-positive and triple-negative breast cancers?

Abstract

To clarify appropriate timing for magnetic resonance examination to predict pathological complete response to neoadjuvant chemotherapy for patients with human epidermal growth factor receptor 2 (HER2)-positive and triple-negative breast cancers in terms of tumor volume change. Between September 2009 and December 2014, 113 women with HER2-positive (n=51) and triple-negative (n=62) invasive breast cancers undergoing neoadjuvant chemotherapy were enrolled. Patients with HER2-positive tumors underwent neoadjuvant chemotherapy with an anthracycline-based regimen followed by docetaxel with trastuzumab. Patients with triple-negative tumors underwent neoadjuvant chemotherapy with anthracycline-based (first in most cases) and taxane-based regimens. Magnetic resonance imaging was performed before neoadjuvant chemotherapy, between the regimens (midpoint examination), and after neoadjuvant chemotherapy (final examination). Response ratio of tumor volume was calculated and receiver-operating characteristic analyses for them for both subtypes were performed at the midpoint and final examinations. Twenty-eight women with HER2-positive tumors (54.9%) and 29 women with triple-negative tumors (46.8%) had pathological complete response. The response ratios were better in cases with pathological complete response than in those without (p=0.0341, p<0.0001). The area under the curve at the final examination was higher than that at the midpoint examination for HER2-positive tumors (p=0.039); whereas for the triple-negative tumors, no significant difference between the two examinations was shown (p=0.5218). Magnetic resonance examination to predict pathological complete response would be feasible after completion of a regimen including trastuzumab for HER2-positive tumors and at the midpoint of neoadjuvant chemotherapy for triple-negative tumors.