A Comparison Of Two Methods For Detecting EGFR T790M Status From Advanced NSCLC Patients With Acquired EGFR-TKI Resistance And Clinical Analysis

Objective To assess the ability of droplet digital PCR and ARMS technology to detect epidermal growth factor receptor (EGFR) T790M mutations from circulating tumor DNA (ctDNA) in advanced non-small cell lung cancer (NSCLC) patients with acquired EGFR-TKI resistance. A sensitive and convenient method for detecting T790M mutation would be desirable to direct patient sequential treatment strategy.Methods We collected 108 Plasma samples and 16 tumor tissues from patients with EGFR-mutant tumors progressing on EGFR TKI therapy in Zhejiang cancer hospital. Every patient was extracted 10ml plasma. DdPCR was used to detect 108 ctDNA and 75 ctDNA was detected by ARMS to determine the T790M mutation status. Tumor tissues from 16 patients were then examined for the presence of T790M using ARMS.Results All of 108 patient plasma samples were detected by ddPCR and 75 were detected by ARMS. And 16 patients experienced re-biopsy were detected by ARMS method. In all,43.7%(47/108) had acquired T790M mutation by ddPCR. In 75 patient plasma samples, comparing ddPCR with ARMS, the rates of T790M mutation were 46.7%(35/75) and 25.3% (19/75) by ddPCR and ARMS, respectively. Of all,16 patients both had tumor and plasma samples, the T790M mutation rates were 56.3%(9/16) by ARMS in tissue and 50.5%(8/16) by ddPCR in plasma ctDNA. Among them, there were two ctDNA T790M mutations by ddPCR but T790M gene negative in tumor tissue by ARMS method. The progression mode tended to gradual progression in T790M mutation patients (40.4%), but the T790M negative was inclined to the mode of dramatic progression (39.3%). For all patients, the median PFS and OS were 12.3 months and 32.8 months, respectively. The patients with T790M-positive tumors had a longer time to disease progression after treatment with EGFR-TKIs (median, 13.1 months vs 10.8 months; P=0.010) and overall survival (median,35.3 months vs 30.3 months; P=0.214) compared with those with T790M-negative patients.Conclusion Our study demonstrates the feasibility and sensitive of detecting EGFR T790M status in plasma samples from NSCLC patients with acquired EGFR-TKI resistance. The ddPCR assay detecting in plasma ctDNAT790M maybe provide an alternative method in some situations. Patients with acquired T790M mutation at the time of progression have gradual progression compared to those without T790M mutation.