Acquired EML4-ALK fusion and EGFR C797S in cis mutation as resistance mechanisms to osimertinib in a non-small cell lung cancer patient with EGFR L858R/T790M.

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) dramatically improve the clinical outcomes of non-small cell lung cancer (NSCLC) patients harboring EGFR -sensitive mutations. Despite the remarkable efficacy of first-and second-generation EGFR TKIs, disease relapse is inevitable. EGFR T790M mutation is a primary contributor to the acquired resistance to first- and second-generation EGFR TKIs. Osimertinib, which is an irreversible third-generation EGFR TKI, was designed for EGFR -activating mutations as well as the EGFR T790M mutation in patients with advanced NSCLC and has demonstrated a convincing efficacy. However, acquired resistance to osimertinib after treatment inevitably occurs. The acquired resistance mechanisms to osimertinib are highly complicated and not fully understood, encompassing EGFR -dependent as well as EGFR -independent mechanisms. Treatment approaches for patients progressing from osimertinib have not been established. We present a case of a stage IV lung adenocarcinoma patient harboring EGFR L858R, acquired T790M after treatment with first-line gefitinib. She then acquired a new EML4-ALK gene fusion after treatment with osimertinib. A combination targeted therapy of osimertinib plus alectinib was initiated, with a progression-free survival of 5 months without any serious adverse reaction. After disease progression, EGFR C797S in cis was detected with a loss of the EML4-ALK fusion by targeted next-generation sequencing. Then therapy was changed to pemetrexed combined with bevacizumab plus camrelizumab, but no obvious effect was observed. The patient had achieved an overall survival of 31 months. As far as we know, this was the first reported case that an EGFR -mutant NSCLC patient-acquired ALK fusion mediating resistance to osimertinib, and sequential EGFR C797S mutation mediating resistance to combined targeted therapy with osimertinib and alectinib. Our case shows that EML4-ALK fusion is a rare but critical resistance mechanism to osimertinib, and C797S mutation in cis may be an underlying mechanism of acquired resistance mutation in double TKIs therapy. Furthermore, molecular detection and rebiopsy play important roles in the selection of therapeutic strategies when the disease progresses.

Wang LS ，Chen SQ ，Zhong X ，Jiao XD ，Liu K ，Qin BD ，Wu Y ，Ling Y ，Duan XP ，Zang YS ... -  《-》

Audit of Molecular Mechanisms of Primary and Secondary Resistance to Various Generations of Tyrosine Kinase Inhibitors in Known Epidermal Growth Factor Receptor-Mutant Non-small Cell Lung Cancer Patients in a Tertiary Centre.

Presently, three generations of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are approved against oncogene addicted EGFR-mutant non-small cell lung cancer (NSCLC). Patients with actionable EGFR mutations invariably develop resistance. This resistance can be intrinsic (primary) or acquired (secondary). This was a retrospective study carried out between January 2016 and April 2021 analysing 486 samples of NSCLC for primary and secondary resistance to first- (erlotinib, gefitinb), second- (afatinib) and/or third-generation (osimertinib) TKIs in EGFR-mutant NSCLCs by next generation sequencing (NGS). Tissue NGS was carried out using the Thermofischer Ion Torrent™ Oncomine™ Focus 52 gene assay; liquid biopsy NGS was carried out using the Oncomine Lung Cell-Free Total Nucleic Acid assay. All cases were previously tested for a single EGFR gene with the Therascreen® EGFR RGQ PCR kit. The results were divided into four groups: (i) group 1: primary resistance to first- and/or second-generation TKIs. This group, with 21 cases, showed EGFR exon 20 insertions, dual, complex mutations and variant of unknown significance, de novo MET gene amplification besides other mutations. (ii) Group 2: primary resistance to third-generation TKIs. This group showed two cases, with one showing dual EGFR mutation (L858R and E709A) and EGFR gene amplification. (iii) Group 3: secondary resistance to first- and second-generation TKIs. This group had 27 cases, which were previously reported negative for EGFR T790M by single gene testing. Significant findings were MET gene amplification in four cases, with one also showing MET exon 14 skipping mutation. Three cases showed small cell change and one showed loss of primary mutation. (iv) Group 4: secondary resistance to third-generation TKIs. The latter group was further subgrouped into group 4A: secondary resistance to osimertinib (third-generation TKI) when offered as second-line therapy after first- and second-generation TKIs on detection of T790M mutation. This group had 15 cases. EGFR T790M mutation was lost in 10 (10/15; 67%) cases and was retained in five cases. Patients with T790M loss experienced early resistance (6.9 months versus 12.6 months mean, P = 0.0024) compared with cases that retained T790M. Two cases gained MET amplification as the resistance mechanisms. Other mutations that were found when EGFR T790M was lost were in FGFR3, KRAS, PIK3CA, CTNNB1, BRAF genes. One case had EML4-ALK translocation. Two cases showed driver EGFR deletion 19, retained T790M and C797S mutation in Cis form. Group 4B: secondary resistance to osimertinib (when given as first-line therapy) in EGFR-mutant NSCLC. This group had three cases. The duration of osimertinib treatment ranged from 11 to 17 months. Two patients showed additional C797S mutation along with primary EGFR mutation. This study shows the wide spectrum of primary and secondary EGFR resistance mechanisms to first, second and third generation of TKIs and helps us to identify newer therapeutic targets that could carry forward the initial advantage offered by EGFR TKIs.

Suryavanshi M ，Jaipuria J ，Mattoo S ，Dhandha S ，Khatri M ... -  《-》

Detection of an EML4-ALK fusion mutation secondary to epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) therapy for lung cancer: a case report.

Ren KH ，Qin WW ，Wang Y ，Peng JC ，Hu WX ... -  《-》

Treatment of Brain Metastases of Non-Small Cell Lung Carcinoma.

Rybarczyk-Kasiuchnicz A ，Ramlau R ，Stencel K 《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

Response to Brigatinib Targeted Therapy in Non-Small Cell Lung Cancer Harboring Epidermal Growth Factor Receptor Exon 19 Deletion, T790M, and cis-C797S Triple Mutations: A Case Report.

Chen ZW ，Lin G ，Shih HJ ，Wu CE ... -  《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》