Target therapy in NSCLC patients: Relevant clinical agents and tumour molecular characterisation

In recent years, a number of new agents that target specific molecular pathways in non-small cell lung cancer (NSCLC) have been investigated. Much effort has been focused on identifying specific markers that are predictive of treatment response, given that a tailored approach would maximise the therapeutic index and cost-effectiveness. Gefitinib and erlotinib are selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) and have produced good results in selected cases in terms of objective response rate and overall survival. At present, EGFR gene mutations are considered the most important predictors of clinical response to TKI therapy and tumour characterisation for these alterations is mandatory prior to any decision making. Echinoderm microtubule-like protein 4-anaplastic lymphoma kinase (EML4-ALK) translocation is another alteration capable of predicting the efficacy of anti-ALK agents, such as crizotinib. Moreover, emerging target agents, such as MET inhibitors, are likely to increase the amount of molecular characterisation required before a decision is made on treatment. The main limiting factor for adequate characterisation of metastatic NSCLC patients is the small quantity of tumour cells available for molecular analysis. In this study, we provided an overview of the most important and clinically relevant target agents in NSCLC patients as well as the most important mechanisms of resistance. The issue of the scant amount of biological samples available for analysis as well as alternative sampling approaches such as plasma- or serum-derived DNA were also examined.