Management and future directions in non-small cell lung cancer with known activating mutations.

Lung cancer accounts for a quarter of all cancer deaths. Non-small cell lung cancer (NSCLC) is currently segregated by the presence of actionable driver oncogenes. This review will provide an overview of molecular subsets of lung cancer, including descriptions of the defining oncogenes (EGFR, ALK, KRAS, ROS1, RET, BRAF, ERBB2, NTRK1, FGFR, among others) and how these predict for response to small molecule tyrosine kinase inhibitors (TKIs) that are either clinically available or in clinical trial development for advanced NSCLC. Particular focus will be placed on subsets with EGFR mutated and ALK rearranged NSCLC. Somatic TKI-sensitizing EGFR mutations (such as exon 19 deletions and L858R substitutions) are the most robust predictive biomarker for symptom improvement, radiographic response, and increment in progression-free survival (PFS) when EGFR TKIs (gefitinib, erlotinib, and afatinib) are used for patients with advanced NSCLC. However, the palliative benefits that EGFR TKIs afford are limited by multiple biologic mechanisms of tumor adaptation/resistance (such as the EGFR-T790M mutation and oncogene bypass tracks), and future efforts toward delaying, preventing, and treating resistance are underway. Similar to EGFR mutations, ALK rearrangements exemplify an oncogene-driven NSCLC that can be effectively palliated with a precision TKI therapy (the multitargeted ALK/MET/ROS1 TKI crizotinib). When resistance to first-line crizotinib therapy occurs, multiple second generation ALK TKIs have demonstrated impressive rates of disease control in clinical trials, and these may modify long-term outcomes for patients with ALK-positive NSCLC. The development of TKIs for other oncogene-driven NSCLCs may expand the portfolio of precision therapies for this recalcitrant cancer.