Multicenter phase 2 study of MRI-guided optimization of neoadjuvant chemotherapy duration in stage II or III HER2-positive breast cancer

Patients with stage II or III HER2-positive breast cancer have good outcomes with the combination of neoadjuvant chemotherapy and HER2-targeted agents. Although increasing the number of chemotherapy cycles improves pathological complete response (pCR) rates, early complete responses are common. The multicenter phase 2 TRAIN-3 trial, at 43 centers in The Netherlands, investigated whether the duration of chemotherapy could be tailored on the basis of radiological response. Patients received a maximum of nine neoadjuvant cycles of paclitaxel, trastuzumab, carboplatin, and pertuzumab. The response was monitored by breast MRI and lymph node biopsy every three cycles. Among the patients with HR-negative disease, 36% had complete radiologic response already after three cycles. These patients underwent surgery after three cycles; 87% of these patients had pCR. The authors conclude that among patients with stage II or III HR-negative, HER2-positive patients, breast MRI could help identify early complete responders.