P3.01-033 Detection of Epidermal Growth Factor Receptor Mutations with Plasma Sample Compared with Tumor Tissue Biopsy in Advanced Lung Adenocarcinoma

Abstract

Personalized treatment based on the molecular markers in tissue of patients have crucial role in clinical practice. However, Obtaining Tumor tissue samples are not always available, and rebiopsy is not easy to do. The liquid biopsy with blood samples will be a good alternative diagnostic method. We compared the detection rate of EGFR mutation detection techniques between matched tumor tissue and peripheral blood sample in patients with lung adenocarcinoma. We collected the paired samples from plasma and paraffin-embedded tumor tissue in patients before EGFR-TKIs treatment or after progression of EFGR-TKIs treatment. EGFR mutation analysis was done by two detection methods. One is the PNAClampTM (Clamp) which is the PNA-based PCR clamping that selectively amplifies only the mutated target DNA sequence as minor portion in mixture with the major wild type DNA sequences. The other is the PANAMutyperTM EGFR kit (Mutyper), which use PNA clamping-assisted fluorescence melting curve analysis to perform mutation detection and genotyping. The tissues were tested by Clamp method, and blood was tested in two ways. We compared the sensitivity of EGFR mutation detection techniques from tumor tissue and plasma circulating tumor DNA in patients. Total patients were thirty two (17 male, 15 female) with advanced stage, mean age was 62.8 years-old, all patients were adenocarcinoma, and fifteen patients were never smoker. EGFR mutation positive rate of tissue was 31.3%. In plasma samples, there were 21.9% in Clamp method and 31.3% in Mutyper method. EGFR plasma detection rate of Mutyper was higher than Clamp. Two patients who showed wild type in tissue Clamp method have EGFR 19 deletion by Mutyper method. Both patients were female never smoker. In two cases, T790M was detected only in tissue but not in liquid biopsy. The overall concordance and degree of agreement between two samples were better in Mutyper (75%, gamma=0.872, p<0.001) than Clamp (71.3%, gamma=0.824 p=0.003). The plasma detection rate and the degree of agreement of Mutyper test were better than Clamp test. This method can be useful to detect EGFR mutation in circulating cell-free DNA sample. Liquid biopsy is an excellent resource, and had additional effect in choosing available drug for EGFR rich lung cancer population.