The standard primary systemic therapy for human epidermal growth factor receptor 2-positive (HER2+) breast cancer is anthracyclines and/or taxanes combined with trastuzumab, which demonstrates a high pathological complete response (pCR). A pCR is a predictive marker of prognosis. However, results slightly differ, depending on the hormone receptor status. The efficacy and tolerability of docetaxel, cyclophosphamide, and trastuzumab (HER-TC) as neoadjuvant chemotherapy (NAC) remain unclear. We performed a prospective multicenter study of HER-TC NAC for HER2+ primary breast cancer.

Eligible patients had a clinical diagnosis of HER2+ invasive breast cancer greater than 1 cm but less than 7 cm and a tumor stage of N0 or N1. T hey were diagnosed between July 2011 and February 2014. For NAC, four cycles of HER-TC (6 mg/kg loading dose, 8 mg/kg, 75, and 600 mg/m) were administered intravenously every 3 weeks. We investigated the pCR of the primary breast tumors. A pCR was defined as no histological evidence of invasive carcinoma or the appearance of only ductal carcinoma in situ.

We enrolled 42 patients. The completion rate for four cycles of HER-TC was 97.6 % (41/42 patients). The overall pCR rate was 43.9 % (18/41 patients). The pCR rate for patients with the luminal HER2 subtype [estrogen receptor (ER)-positive+, HER2+] and the HER2-enriched subtype (ER-, HER2+) was 40.0 % (8/20 patients) and 47.6 % (10/21 patients), respectively. A pCR was achieved with nearly the same probability for each subtype.

Four cycles of HER-TC may be a NAC option for HER2-positive breast cancer.