A systematic review of dual targeting in HER2-positive breast cancer

BackgroundHuman epidermal growth factor receptor 2 (HER2) is overexpresed in 15-20% of all breast cancers. Treatment with trastuzumab has led to an improved outcome and prolonged survival of HER2-positive breast cancer patients and today the drug is established as standard of care in both the adjuvant and metastatic settings. However, trastuzumab resistance is common and a major focus in the treatment of HER2-positive breast cancer has been developing therapeutic agents to either potentiate the effect of trastuzumab or to target cells which have become resistant to trastuzumab. The present review addresses efficacy and toxicity of dual targeting in HER2-positive breast cancer.Materials and methodsA computer-based literature search was carried out using PubMed; data reported at international meetings and clinicaltrials.gov was included.ResultsThis paper describes efficacy and safety of lapatinib, pertuzumab or trastuzumab-DM1 in combination with trastuzumab in the (neo)adjuvant and metastatic settings. Furthermore, combinations of trastuzumab and drugs targeting the downstream pathway are described.ConclusionDual blockade is likely to represent a substantial advance for patients with HER2-positive breast cancer. However, the relevant subpopulation remains to be defined and side effects including cardiotoxicity might be a limiting factor to the use. There is an urgent need for prospective biomarker-driven trials to identify patients for whom dual targeting is cost-effective.