Abstract: Exploring resistance mechanisms in patients with EGFR -mutant non-small-cell lung cancer (NSCLC) upon disease progression on EGFR tyrosine kinase inhibitors (TKIs) has been an area of great interest as it may lead to effective next-line treatment strategies. Here we report a case of emergent MET  amplification detected in a tumor sample from a patient with NSCLC harboring EGFR L858R mutation after disease progression on erlotinib. The patient subsequently had a sustained partial response to a combination of full-dose osimertinib and crizotinib with excellent tolerance but eventually had central nervous system (CNS) progression. Comprehensive genomic profiling performed on the resected brain sample continued to demonstrate MET  amplification as an acquired resistance mechanism. A review of literature shows several groups have utilized similar combination regimens (erlotinib or osimertinib + crizotinib or cabozantinib), albeit with various dosing to target MET  alterations in patients with EGFR -mutant NSCLC. As more actionable resistance mechanisms are identified, we envision combination TKI therapy will be readily adopted in clinical practice. Our case report adds to a growing body of evidence that combination osimertinib and crizotinib should be recommended to EGFR -mutant NSCLC patients with emergent MET  amplification as acquired resistance. More importantly, as crizotinib has limited brain penetration, developing next-generation MET inhibitors with better CNS activity is urgently needed.
Keywords: resistance, TKI, erlotinib, cabozantinib, CGP, gefitinib