EGFR T790M Mutation: A Double Role in Lung Cancer Cell Survival?

Abstract:Even though lung cancer patients harboring a mutation in the epidermal growth factor receptor (EGFR) gene exhibit an initial dramatic response to EGFR tyrosine kinase inhibitors (EGFR-TKIs), acquired resistance is almost inevitable after a progression-free period of approximately 10 months. A secondary point mutation that substitutes methionine for threonine at amino acid position 790 (T790M) is a molecular mechanism that produces a drug-resistant variant of the targeted kinase. The T790M mutation is present in about half of the lung cancer patients with acquired resistance, and reported to act by increasing the affinity of the receptor to adenosine triphosphate, relative to its affinity to TKIs. Nevertheless, several lines of evidence indicate that the T790M mutation confers growth advantage to cancer cells, and it was shown that mice expressing tetracycline-inducible EGFR transgenes harboring the T790M mutation develop lung tumors. Thus, T790M mutation seems to play a double role in the survival of lung cancer cells. Several second-generation EGFR-TKIs are currently being developed to overcome the acquired resistance caused by the T790M mutation. MET (met proto-oncogene) amplification or activation of IGF1R are reported as alternative mechanisms for acquired resistance to EGFR-TKIs. Clarification of the pathways leading to acquired resistance is essential to maximize the efficacy of EGFR-TKI therapy for patients with lung cancer

Post-Progression Survival Is Strongly Associated with Overall Survival in Patients Exhibiting Postoperative Relapse of Non-Small-Cell Lung Cancer Harboring Sensitizing EGFR Mutations

Background and Objective: Patients with advanced non-small-cell lung cancer (NSCLC) harboring sensitizing epidermal growth factor receptor (EGFR) mutations show a good response to EGFR-tyrosine kinase inhibitors (EGFR-TKIs). The subsequent treatments influence the evaluability of the efficacy of front-line therapy on overall survival (OS). Consequently, we evaluated the associations of relapse-free survival (RFS) and post-progression survival (PPS) with OS in patients who exhibited postoperative relapse of EGFR-mutated NSCLC. Materials and Methods: We analyzed the data of 35 patients with EGFR-mutated NSCLC who underwent complete resection between January 2007 and June 2019. The correlations of RFS and PPS with OS were evaluated at the individual patient level. Results: Linear regression and Spearman’s rank correlation analyses demonstrated that the PPS highly correlated with OS (r = 0.91, p < 0.05, R2 = 0.85), whereas the RFS weakly associated with OS (r = 0.36, p < 0.05, R2 = 0.25). Age and performance status at relapse were significantly associated with PPS. Conclusion: Overall, PPS was more strongly and significantly associated with OS than RFS. These results suggest that the OS of our cohort may be affected by treatments, besides postoperative relapse. However, larger-scale prospective studies are needed to confirm these results