Assessment of EGFR mutation status in matched plasma and tumor tissue of NSCLC patients.

Abstract

e20032 Background: Tumor tissue is currently used for EGFR testing non-small cell lung cancer (NSCLC) patients, but the detection of circulating tumor DNA (ctDNA) is being actively investigated as a new method for the detection and longitudinal monitoring of actionable mutations in plasma samples. Around 30% patients with EGFR mutation presented inconsistent status of EGFR mutation between in tissues and plasma. We compared EGFR mutation detection in circulating tumor DNA from blood to that in matched tissue. Methods: EGFR mutation status were assessed by the Human EGFR Gene Mutations Detection Kit (Beijing ACCB Biotech Ltd.) both in tissue and plasma. Retrospective analysis to evaluate the concordance of tissue and plasma EGFR determination for assessing eligibility for EGFR-TKIs therapy in NSCLC patients. 10 mL tubes of blood were collected from patients who never had been treated by EGFR TKI, and plasma circulating tumor DNA were extracted from plasma by Biomark Circulating DNA Kit. Qubit2.0 Fluorometer was used to make plasma circulating DNA tumor quantitation. The concentration of final DNA sample is ≦2ng/μl. Results: A total of 224 NSCLC patients were detected by Amplification Refractory Mutation System (ARMS), with 92 tissue positive and 49 blood positive. Results showed 53.3% sensitivity in overall samples, but 81.4% sensitivity in ⅢB~Ⅲ patients. The specificity is 100%. Conclusions: The high sensitivity and specificity between tissue and plasma EGFR determination supports the blood-based EGFR mutation testing to determinate the eligibility of NSCLC patients for EGFR-TKIs treatment, especialy in ⅢB~Ⅲ NSCLC patients. Blood, in particular plasma, is a good screening substitute when tumor tissue is absent or insufficient for testing EGFR mutations to guide EGFR TKIs treatment in patients with NSCLC. EGFR mutation positivity in blood could be used to recommend EGFR TKIs treatment, but the blood negativity should be confirmed with other sample, biopsy tissue, pleural effusion, etc..