Neoadjuvant therapy of early stage human epidermal growth factor receptor 2 positive breast cancer: latest evidence and clinical implications.

Neoadjuvant therapy in human epidermal growth factor receptor 2 (HER2)-positive breast cancer is exactly the paradigm of targeted therapy and a suitable setting to develop and test rapidly novel therapies in early stages. Moreover, neoadjuvant approaches provide a significant source of tumour tissue to identify molecular heterogeneity and potential predictive biomarkers of response. The addition of trastuzumab to primary chemotherapy revolutionized the treatment of this tumour subtype, increasing pathological complete response rate (pCR) that, even with its limitations, has also been shown to be an early marker of survival in HER2-positive disease. HER2-positive breast cancer is a biological heterogeneous disease with different characteristics and clinical outcomes. Multiple promising anti-HER2 drugs with nonoverlapping mechanisms of action have recently been developed. Combined administration of two different HER2-targeted agents, that is, trastuzumab with lapatinib or pertuzumab, and primary chemotherapy shows enhanced antitumour activity, with an increase in pCR to values never reached in the past. Moreover, results of recent studies show that the combination of targeted therapy alone (dual HER2 blockade with or without endocrine therapy) also has activity in a substantial percentage of patients, eradicating HER2-positive tumours without chemotherapy and with a favourable toxicity profile. It is still necessary to be able to select the appropriate group of patients who can avoid chemotherapy (approximately 25%), and to establish robust predictive biomarkers of response or resistance to the anti-HER2 approach. Neoadjuvant therapy represents an enormous step forward in HER2-positive breast cancer. The results of the most relevant neoadjuvant studies and latest evidence are described in this review, though new questions have emerged.