Abstract
When tumor biopsies from patients (pts) with advanced NSCLC yield infeasible or insufficient for successful molecular subtyping, plasma cfDNA genotyping has been widely adopted due to its convenience and high positive predictive value. However, a different assay sensitivity makes the optimal choice more difficult. In this study, we have analyzed the clinical utility of two different plasma-based EGFR-mutation (mEGFR) tests in pts with advanced NSCLC. We prospectively enrolled consecutive pts with advanced NSCLC with adequate tissue before EGFR genotyping in single institution (June 2017-December 2018). EGFR tissue genotyping was performed using peptide nucleic acid (PNA) based PANAMutyper R EGFR assay (PANAGENE, Daejeon, Korea). EGFR plasma genotyping was performed using Cobas EGFR Mutation Test v2(Roche, Mannheim, Germany) and PANAMutyper R EGFR assay. All pts provided informed consent. We included 72 patients. 44 (61%) were treatment naïve. Overall sensitivity for mEGFR positive was 52% (23/44) from tissue, but 34% (15/44) from Cobas and 30% (13/44) from PANAMutyper. Among 21 pts with tissue mEGFR-negative, plasma mEGFR test found additional 2 pts with mEGFR positive from Cobas and 1 pts from PANAMutyper. EGFR sensitivity with tissue increased to 57% and 55% when combining with plasma by Cobas and PANAMutyper, respectively. Concordance rate of tissue mEGFR was same as 73% with Cobas and PANAMutyper (kappa 0.46). Among 28 pretreated mEGFR-positive advanced NSCLC, sensitivity for mEGFR positive was 71% (20/28, include 6 cases of T790M) from tissue re-biopsy, and 68% (19/28, include 8 cases of T790M) from Cobas and 57% (16/28, include 6 cases of T790M) from PANAMutyper. Cobas plasma mEGFR test found additional 2 pts with T790M. T790M sensitivity with tissue (30%) increased to 40% for both tissue and plasma by Cobas. In pretreated setting, concordance rate of tissue mEGFR was 96% with Cobas (kappa 0.92) and 86% with PANAMutyper (kappa 0.70). In pts with treatment naïve advanced NSCLC, sensitivity for tissue mEGFR was higher than plasma mEGFR genotyping. Though plasma mEGFR test found additional mEGFR positive patients, overall sensitivity was slightly increased when combining both methods. In pts with pretreated mEGFR-positive, overall sensitivity for tissue mEGFR was similar with Cobas plasma mEGFR genotyping with high concordance rate.
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