Response to EGFR/NTRK/MET Co-Inhibition Guided by Paired NGS in Advanced NSCLC With Acquired EGFR L858R/T790M/C797S Mutations.

Abstract

EGFR tyrosine kinase inhibitors (TKIs) have significantly improved clinical outcomes for patients with non-small cell lung cancer (NSCLC) harboring EGFR-activating mutations. However, resistance to TKI therapy often develops due to secondary EGFR mutations or the activation of bypass signalling pathways. Next-generation sequencing (NGS) can efficiently identify actionable genetic alterations throughout treatment. MET amplification is a well-established off-target resistance mechanism. Additionally, rarer mechanisms, such as NTRK1 gene fusions, have been reported. This report highlights a case of a 58-year-old male diagnosed with bone-metastatic NSCLC harboring the EGFR L858R mutation. After receiving dacomitinib and almonertinib sequentially, plasma-based NGS revealed the emergence of EGFR T790M-trans-C797S mutations, prompting a switch to a combination therapy of almonertinib and gefitinib. Upon disease progression, repeat NGS identified EGFR T790M-cis&trans-C797S mutations and a novel POT1::NTRK3 fusion in the blood. The fusion retained a complete NTRK kinase domain without frameshift variants, making it a target for treatment. Larotrectinib was incorporated into the dual EGFR-TKI regimen, forming a triplet therapy. Although this resulted in grade 3 dermatitis, the condition resolved after discontinuing gefitinib. At multiorgan progression, matched tissue- and plasma-based NGS identified MET amplification. Subsequently, the patient was started on a triple-inhibition regimen targeting EGFR, NTRK, and MET, which achieved a partial response with favorable tolerability. This is the first reported case of a novel, targetable POT1::NTRK3 fusion as a potential off-target mechanism mediating EGFR-TKI resistance, occurring alongside MET amplification in a patient with NSCLC harboring acquired EGFR L858R/T790M/C797S mutations. Concomitant inhibition of EGFR, NTRK, and MET was safe and resulted in a significant response, underscoring the importance of precision medicine guided by matched NGS.