Mutation Spectrum of EGFR From 21,324 Chinese Patients With Non-Small Cell Lung Cancer (NSCLC) Successfully Tested by Multiple Methods in a CAP-Accredited Laboratory

Abstract

Genotyping epidermal growth factor receptor (EGFR) gene in patients with advanced non-small cell lung cancers (NSCLC) is essential for identifying those patients who may benefit from targeted therapies. Systemically evaluating EGFR mutation detection rates of different methods currently used in clinical setting will provide valuable information to clinicians and laboratory scientists who take care of NSCLC patients. This study retrospectively reviewed the EGFR data obtained in our laboratory in last 10 years. A total of 21,324 NSCLC cases successfully underwent EGFR genotyping for clinical therapeutic purpose, including 5,244 cases tested by Sanger sequencing, 13,329 cases tested by real-time PCR, and 2,751 tested by next-generation sequencing (NGS). The average EGFR mutation rate was 45.1%, with 40.3% identified by Sanger sequencing, 46.5% by real-time PCR and 47.5% by NGS. Of these cases with EGFR mutations identified, 93.3% of them harbored a single EGFR mutation (92.1% with 19del or L858R, and 7.9% with uncommon mutations) and 6.7% harbored complex EGFR mutations. Of the 72 distinct EGFR variants identified in this study, 15 of them (single or complex EGFR mutations) were newly identified in NSCLC. For these cases with EGFR mutations tested by NGS, 65.3% of them also carried tumor-related variants in some non-EGFR genes and about one third of them were considered candidates of targeted drugs. NGS method showed advantages over Sanger sequencing and real-time PCR not only by providing the highest mutation detection rate of EGFR but also by identifying actionable non-EGFR mutations with targeted drugs in clinical setting.

Keywords: EGFR mutation testing; Sanger sequencing; next-generation sequencing; non-small cell lung cancer; real-time PCR.

FIGURE 1

Mutation detection rates for EGFR. (A) The average mutation detection rates for EGFR obtained by Sanger sequencing, real-time PCR, and NGS methods. (B) EGFR mutation detection rates in NSCLC samples with 1–20% TCC by real-time PCR and NGS.

FIGURE 2

EGFR mutation patterns. (A) An overview of EGFR mutations present in 8,979 cases with single EGFR mutations. (B) A summary of EGFR mutations present in 642 cases with complex EGFR mutations.

FIGURE 3

Non-EGFR genes carrying mutations identified by NGS. (A) Genes carrying targetable driver mutations identified in the 2,751 NSCLC cases by NGS. (B) Non-EGFR genes carrying mutations identified by NGS in 1,308 EGFR-positive cases by NGS.