Rare mutations of epidermal growth factor receptor in epidermal growth factor receptor-tyrosine kinase inhibitor-naive non-small cell lung carcinoma and the response to erlotinib therapy

ABSTRACT

Context Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are considered to be effective treatments for advanced NSCLC patients with sensitizing EGFR mutations. There are many complex and rare mutations in the EGFR gene. The efficacy of the first-generation EGFR-TKI (erlotinib) is unknown for tumors harboring rare EGFR mutations. Aims: The purpose of this study was to investigate the clinical significance of rare EGFR mutations in EGFR-TKI-naive patients and the efficacy of erlotinib. Settings and Design: Istanbul University, Istanbul Medical Faculty, Department of Medical Oncology, Istanbul/Turkey, and retrospective observational study. Subjects and Methods: We retrospectively analyzed 117 non-small cell lung cancer (NSCLC) patients with EGFR mutations who had not previously used EGFR-TKIs. Exons 18–21 of EGFR were analyzed by polymerase chain reaction and subjected to direct sequencing methods. Statistical Analysis Used Survival estimates were calculated by the Kaplan–Meier method using SPSS 25 software (IBM SPSS, Chicago, USA). Results: Of 117 patients who had EGFR mutations, 23 patients had rare and complex EGFR mutations. Only 9 of them were treated with erlotinib. Three patients (3.5%) with exon 20 mutations received erlotinib. Two with EGFR-p. Q787Q (SNP ID, rs10251977; c.2361G>A) synonymous mutation in exon 20 were responsive to erlotinib therapy in the second-line setting after first-line chemotherapy. To the best of our knowledge, the present two cases are the first to be reported with lung adenocarcinoma with EGFR-p. Q787Q synonymous mutation responding to erlotinib. Conclusion: NSCLC patients harboring rare EGFR mutations generally did not show consistent or favorable responses to EGFR-TKI. We suggest that this rare synonymous mutation (EGFR-p. Q787Q) is a sensitive EGFR mutation in NSCLC