Overcoming resistance to targeted therapies in NSCLC: current approaches and clinical application

The discovery that a number of aberrant tumorigenic processes and signal transduction pathways are mediated by druggable protein kinases has led to a revolutionary change in nonsmall cell lung cancer (NSCLC) treatment. Epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) are the targets of several tyrosine kinase inhibitors (TKIs), some of them approved for treatment and others currently in clinical development. First-generation agents offer, in target populations, a substantial improvement of outcomes compared with standard chemotherapy in the treatment of advanced NSCLC. Unfortunately, drug resistance develops after initial benefit through a variety of mechanisms. Novel generation EGFR and ALK inhibitors are currently in advanced clinical development and are producing encouraging results in patients with acquired resistance to previous generation agents. The search for new drugs or strategies to overcome the TKI resistance in patients with EGFR mutations or ALK rearrangements is to be considered a priority for the improvement of outcomes in the treatment of advanced NSCLC.

Therapeutic management of ALK+ nonsmall cell lung cancer patients

With therapeutic approaches based on oncogene addiction offering significant anticancer benefit, the identification of anaplastic lymphoma kinase (ALK) rearrangements is a key aspect of the management of lung cancers. The EML4-ALK gene fusion is detected in 4-8% of all lung cancers, predominantly in light smokers or nonsmokers. Crizotinib, the first agent to be approved in this indication, is associated with a median progression-free survival of 10.9 months when given as first-line treatment and 7.7 months when administered after chemotherapy. Median overall survival with crizotinib in the second-line setting is 20.3 months. Second-generation ALK inhibitors are currently being evaluated, with early studies giving impressive results, notably in patients resistant to crizotinib or with brain metastases. Among available chemotherapies, pemetrexed appears to be particularly active in this population. Despite this progress, several questions remain unanswered. What detection strategies should be favoured? What underlies the mechanisms of resistance and what options are available to overcome them? What are the best approaches for progressing patients? This review provides an overview of current data in the literature and addresses these questions.