Comparison of epidermal growth factor receptor (EGFR) gene T790M mutation by droplet digital PCR and Super-ARMS PCR in plasma ctDNA samples of non-small cell lung cancer patients with the resistance to EGFR-tyrosine kinase inhibitor

Abstract

Objective: To compare droplet digital PCR (ddPCR) and Super-amplification refractory mutation system (ARMS) in the detection of T790M mutation of epidermal growth factor receptor (EGFR) in the plasma of non-small cell lung cancer patients who had developed resistance to EGFR tyrosine kinase inhibitor (TKI) , and to investigate the clinical application of ddPCR. Methods: Plasma samples were collected from non-small cell lung cancer patients who had acquired EGFR-TKI resistance at Shanghai Pulmonary Hospital, Tongji University, from May 2017 to November 2017. Extracted ctDNA was analyzed by ddPCR and Super-ARMS to evaluate the T790M mutation status of EGFR gene. Results: A total of 37 patients with activating EGFR mutation that acquired resistance to EGFR-TKI were selected in the study, including 17 male and 20 female with a median age of 64 years (range 40-83 years). Before TKI treatment, all the patients harbored EGFR inhibitor sensitive mutations but without T790M mutation. After acquiring resistance to EGFR-TKI treatment, the T790M mutation rate detectable by ddPCR was 45.9% (17/37). In contrast, the mutation rate of T790M detectable by Super-ARMS was 35.1% (13/37, P<0.05). For the 13 positive cases detected by Super-ARMS (ΔCt<8), they were all positive by ddPCR assay; Among the 10 negative cases detected by Super-ARMS (ΔCt≥8), there were 3 cases positive by ddPCR assay. For patients without ΔCt by Super-ARMS assay, there was one weak positive case detectable by ddPCR assay. Among 17 EGFR T790M positive patients, 9 received EGFR inhibitor Osimertinib treatment, and 7 of them had good therapeutic response after the treatment. Conclusions: While a significant correlation between the two methods is shown. ddPCR is more sensitive than Super-ARMS in the detection of EGFR T790M mutation, indicating that it is a better method in guiding target drug therapy of non-small cell lung cancer patients after acquiring the resistance to EGFR-TKI.