A Case of Primary Resistance to Gefitinib due to Novel Deletion-Insertion Mutation of EGFR Exon 19 in NSCLC

In recent years, molecularly targeted therapies against specific oncogenes based on accurate gene analysis have been widely used in the treatment of patients with NSCLC. Gefitinib and erlotinib, as two well-known tyrosine kinase inhibitors (TKIs), have been used as the first-line treatment for patients with metastatic NSCLC harboring a deletion mutation in EGFR exon 19 or L858R point mutations in EGFR exon 21. Several large randomized trials indicated superior progression-free survival with single-agent erlotinib or gefitinib over platinum-based chemotherapy among patients with EGFR-sensitive mutations1Sukrithan V. Deng L. Barbaro A. Cheng H. Emerging drugs for EGFR-mutated non-small cell lung cancer.Expert Opin Emerg Drugs. 2018; 20: 1-12Google Scholar; nevertheless, primary resistance to EGFR TKIs is not fully understood.2Wang J. Wang B. Chu H. Yao Y. Intrinsic resistance to EGFR tyrosine kinase inhibitors in advanced non-small-cell lung cancer with activating EGFR mutations.Onco Targets Ther. 2016; 9: 3711-3726Crossref PubMed Scopus (89) Google Scholar Here, we report a case of lung adenocarcinoma in which primary resistance to gefitinib treatment was caused by a unique deletion-insertion mutation of EGFR exon 19. A 61-year-old women who had never smoked came to our hospital with asthma and cough that had persisted for more than 10 days. Computed tomography (CT) examinations revealed space-occupying lesions in the left lung that were determined by pathological diagnosis of an aspiration biopsy sample to be lung adenocarcinoma (Figs. 1A and 2A). To determine the metastasis of tumors, the patient underwent positron emission tomography–CT scanning, which confirmed high-glucose metabolic loci in the left lung, hilum of the left lung, and mediastinal lymph nodes, suggesting metastasis (Fig. 1C). Then, amplification refractory mutation system (ARMS)–polymerase chain reaction (PCR) using a collected pathological paraffin tissue section sample suggested a deletion mutation of EGFR exon 19 (Fig. 3B). After daily oral administration of gefitinib for 4 months, the patient was hospitalized again with asthma, cough, blood in the sputum, and pain in the chest. A repeat CT scan showed enlargement of the tumors in the left lung, hilum of the left lung, and mediastinal lymph nodes accompanied by pleural effusion and inflammation (Fig. 1B). To clarify the reason of resistance to gefitinib, next-generation sequencing (NGS) was performed to detect lung cancer–related gene mutations by using new aspiration biopsy tissue in the left lung, which also confirmed the positive detection of lung adenocarcinoma by pathological examination (Fig. 2B). The result of NGS suggested a novel deletion-insertion mutation of EGFR exon 19 (p.Glu746_Leu747delinsThrPro, c.2235_2240delGGAATTinsAACCCC [reference sequence NM_005228.3]) (Fig. 3A). To confirm the NGS result, we used the Sanger sequencing method to analyze the patient’s pathological tissue sample, which had been used with the aforementioned ARMS-PCR procedure. Sanger sequencing confirmed this unique deletion-insertion mutation in EGFR exon 19 (Fig. 3C). From then, the patient started to receive treatment consisting of pemetrexed plus carboplatin.Figure 2Positive detection of adenocarcinoma cells in an aspiration biopsy sample of the lump in the left lung (A) and the second aspiration biopsy tissue sample in the left lung after 4 months of gefitinib treatment (B).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3(A) Next-generation sequencing reads in the EGFR exon 19 regions from the second aspiration biopsy tissue were visualized by using the Integrated Genomics Viewer. (B) Amplification refractory mutation system–polymerase chain reaction using the first aspiration biopsy tissue suggested a deletion mutation of EGFR exon 19. (C) Confirmation of the deletion-insertion mutation of EGFR exon 19 by Sanger sequencing analysis. The upper image is the mutation sequence, and the lower image is the wild type sequence.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The evidence presented in this case suggests that this novel deletion-insertion mutation of EGFR exon 19 may be one important mechanism mediating the primary resistance of NSCLC cells to gefitinib. The first-generation EGFR TKIs, such as gefitinib and erlotinib, bind noncovalently to EGFR tyrosine kinase sites, competing with adenosine triphosphate.1Sukrithan V. Deng L. Barbaro A. Cheng H. Emerging drugs for EGFR-mutated non-small cell lung cancer.Expert Opin Emerg Drugs. 2018; 20: 1-12Google Scholar We hypothesize that the novel gene mutation found in this report may reduce the affinity between EGFR TKIs and EGFR protein, and we will further explore the mechanism of this novel deletion-insertion mutation of EGFR exon 19 leading to ineffectiveness of EGFR TKIs in NSCLC cells. Moreover, with patients with NSCLC may benefit more from NGS than from ARMS-PCR as their first genetic test, as the NGS technology is more precise, sensitive, and comprehensive than the ARMS-PCR method. This work was supported by the Henan Programs for Science and Technology Development (grant 162300410117).