Detection of epidermal growth factor receptor mutation in plasma as a biomarker in Chinese patients with early-stage non-small cell lung cancer

PURPOSE: This preplanned exploratory analysis was conducted to reveal the true status of correlation between tissue and plasma detection for early-stage non-small cell lung cancer (NSCLC) epidermal growth factor receptor (EGFR) mutations, knowing that specific subgroups of NSCLC patients may be potential candidates for EGFR mutation analysis by using plasma samples. MATERIALS AND METHODS: Tissue samples were surgically resected from 198 patients with stage I–IV NSCLC, where stage I(A) to III(A) accounted for 92.4%. EGFR mutations in all these tissues were positive. Paired plasma EGFR mutations were detected by real-time polymerase chain reaction; concentration of cell-free DNA (cfDNA) in plasma was measured by ultraviolet spectrophotometry. RESULTS: EGFR-activating mutation was detected in 34 plasma samples, and their mutation types were matched with that in tissue. The sensitivity of EGFR mutation for the 198 paired tissue and plasma samples was 17.2%. The sensitivity positively correlated with disease stage and negatively correlated with tumor differentiation. The sensitivity of stage I(A), I(B), II(A), II(B), and III(A) was 1.6%, 7.9%, 11.1%, 20%, and 33.3%, respectively; the sensitivity of high differentiation was 0% versus 36.8% for poor differentiation. There was no correlation between plasma cfDNA concentration and patient characteristics. CONCLUSION: We recommend using plasma cfDNA as a biomarker in stage III(A) or poorly differentiated tumors for gene diagnosis, especially in patients whose tissue samples cannot be obtained by surgery. Plasma samples can really reflect the patients’ EGFR mutation types and may contain comprehensive genotypic information that comes from different parts of the tumor than tissue specimens. The concentration of plasma cfDNA does not vary with patient characteristics.