BACKGROUND: A previously published prospective randomized phase 3 trial showed that administration of 24 weeks of primary systemic chemotherapy (PST) with paclitaxel and FEC(75) (fluorouracil, epirubicin, cyclophosphamide) concurrently with trastuzumab in patients with HER2-positive primary breast cancer resulted in a 60% pathologic complete response rate (PCR) with no associated severe cardiac toxicity.