Acquired EGFR T790M Mutation After Relapse Following EGFR-TKI Therapy: A Population-based Multi-institutional Study.

AIM: To describe the prevalence and determinants of acquired epidermal growth factor receptor (EGFR) T790M gene mutation in a clinical practice setting. MATERIALS AND METHODS: We performed a retrospective chart review study between January 2013 and November 2017 across multiple institutes, covering a population of 3 million people. RESULTS: We reviewed the charts of 233 patients non-small cell lung cancer with EGFR mutations. Of them, 99 (42.5%) patients had acquired T790M mutations in EGFR. Patients ≥75 years old and patients with an exon 19 deletion had higher rates of acquired T790M mutation than did younger patients and those with an exon 21 L858R mutation. In 75 patients treated with afatinib, 34 (45.3%) patients had acquired T790M mutation. The sensitivity of T790M mutation detection was lower in plasma specimens than in biopsy specimens. CONCLUSION: This population-based study confirms previous studies and highlights potential determinants of acquired T790M mutation to be considered in clinical practice.