EGFR T790M detection in formalin‐fixed paraffin‐embedded tissues of patients with lung cancer using RNA‐based in situ hybridization: A preliminary feasibility study

Abstract

Background Following drug resistance in patients with lung cancer treated by EGFR TKIs, a biopsy is required to obtain sufficient cancer tissue for T790M detection in order to select potential beneficiaries suitable for third‐generation EGFR TKIs, such as osimertinib. The purpose of this study was to explore the feasibility of using a new in situ analysis technique based on RNA target sequences to detect EGFR T790M in lung cancer. Methods A total of 28 formalin‐fixed paraffin‐embedded (FFPE) samples from 24 lung adenocarcinoma patients archived in Peking Union Medical College Hospital from 2015 to 2016 were collected. The BaseScope T790M detection technique by in situ hybridization on FFPE slides was used to analyze the mutation of EGFR T790M, and then the results were compared with the data acquired by Scorpions ARMS assay, which is the so‐called gold standard for EGFR gene mutation testing. The sensitivity and specificity of the BaseScope T790M detection technique were preliminarily evaluated. Results Of the 28 FFPE specimens, the average proportion of T790M‐positive cells was 35.78% ± 17.68% in 18 samples with EGFR T790M, confirmed by Scorpions ARMS assay, Compared with real‐time PCR assay, the sensitivity and specificity of BaseScope T790M were all 100% in our cohort. Conclusion BaseScope T790M assay could be completed on only one FFPE slide and the visualized molecular result overplayed with histomorphological information perfectly, so it may be the alternative method for EGFR T790M evaluation. BaseScope assay has potential clinical utility, and it will be necessary to carry out validation with a large number of cases.

The Status of the EGFR T790M Mutation is associated with the Clinical Benefits of Osimertinib Treatment in Non-small Cell Lung Cancer Patients: A Meta-Analysis

“…Osimertinib is effective for patients who have EGFR T790M mutations and can exert selective pressure, resulting in an increase in pre-existing T790M wild-type clones with additional EGFR-independent resistance mechanisms. This makes them more visible than T790M mutant cells in primary "T790M positive tumors", which may further result in the loss of T790M under resistance to Osimertinib [30]. Consistent with this hypothesis, we statistically analyzed the results of second-generation sequencing of tumors that have lost T790M mutations and found multiple EGFR-independent resistance mechanisms, such as alternative signaling pathways for bypassing activation and histological transformation [31,32].…”

Biological significance of KRAS mutant allele expression in ovarian endometriosis

“…Previously, there are two studies that show the potential of this in situ technology for clinical applications in oncology field. The one demonstrated the prognostic value of POLE mutation identified by this assay in uterine cancer, 30 and the other study showed the assay as a tool for discovery of biomarker of EGFR inhibitor in lung cancer 31 . Moreover, this method could be applied as a biomarker for KRAS inhibitor which has been recently clinically applied to cancers with KRAS p.G12C 32,33 .…”

“…The one demonstrated the prognostic value of POLE mutation identified by this assay in uterine cancer, 30 and the other study showed the assay as a tool for discovery of biomarker of EGFR inhibitor in lung cancer. 31 Moreover, this method could be applied as a biomarker for KRAS inhibitor which has been recently clinically applied to cancers with KRAS p.G12C. 32,33 Therefore, RNA-based in situ mutation detection assay can be used for a detection of biomarker and a prediction of prognosis in clinical practice.…”

A Real-World Analysis of Patients with Untreated Metastatic Epidermal Growth Factor Receptor (EGFR)-Mutated Lung Adenocarcinoma Receiving First-Line Erlotinib and Bevacizumab Combination Therapy

“…The EGFR-T790M point mutation accounts for most of the genomic alterations (30–60%) leading to secondary acquired resistance in EGFR-mutated NSCLC patients receiving a course of erlotinib therapy [ 32 , 33 ]. Tissue rebiopsy for EGFR-T790M mutation tests is often required in these patients with acquired resistance to erlotinib therapy [ 32 , 33 ].…”

“…The EGFR-T790M point mutation accounts for most of the genomic alterations (30–60%) leading to secondary acquired resistance in EGFR-mutated NSCLC patients receiving a course of erlotinib therapy [ 32 , 33 ]. Tissue rebiopsy for EGFR-T790M mutation tests is often required in these patients with acquired resistance to erlotinib therapy [ 32 , 33 ]. The third-generation EGFR-TKI osimertinib is an effective subsequent targeted therapy for lung adenocarcinoma patients with secondary EGFR-T790M mutations after erlotinib treatment [ 34 ].…”