Value of droplet digital polymerase chain reaction in detecting epidermal growth factor receptor mutations in peripheral blood circulating tumor DNA of patients with non-small cell lung cancer / 肿瘤研究与临床

ABSTRACT

Objective:To analyze the value of droplet digital polymerase chain reaction (ddPCR) in detecting epidermal growth factor receptor (EGFR) mutations in peripheral blood circulating tumor DNA (ctDNA) of patients with non-small cell lung cancer (NSCLC).Methods:Peripheral blood samples of 63 patients with NSCLC who were treated in Shanxi Provincial Cancer Hospital from August 2018 to March 2019 were collected, and EGFR sensitive mutations in peripheral blood of patients were detected by ddPCR, and the results were compared with the results of amplification refractory mutation system polymerase chain reaction (ARMS-PCR). Kappa test was used to analyze the consistency of the two methods.Results:The EGFR sensitive mutations were found in 31 cases (49.2%) by ddPCR in peripheral blood of 63 patients with NSCLC. Among them, 1 case (1.6%) had G719X, 12 cases (19.0%) had E19-Del, 11 cases had T790M (17.5%), 7 cases (11.1%) had L858R. Seven cases (22.6%) of the patients had double mutations. In comparison, the above 4 mutations were found in 26 cases (41.3%) by the ARMS-PCR method, with 0 case, 12 cases (19.0%), 6 cases (9.5%), and 8 cases (12.7%), respectively, including 5 cases (19.2%) with double mutations. L858R in one case was positive when detected by ARMS-PCR, while it was negative when detected by ddPCR. The consistency rate of the two methods was 90.3% (κ = 0.8, P < 0.05). The median abundance of EGFR mutations in peripheral blood ctDNA of 31 cases was 1.7% (range 0.04%-23.60%). The median abundance of E19-Del was 2.50% (0.35%-22.70%), that of T790M was 0.6% (0.04%-14.00%), and that of L858R was 2.3% (0.20%-23.60%). Ten cases with the abundance of EGFR mutations < 1% when detected by ddPCR, accounting for 32.6% (10/31) of total patients with mutations, but only 5 cases of them were detected by ARMS-PCR. The detection rate of T790M by ddPCR in patients who had received tyrosine kinase inhibitor (TKI) and had acquired drug resistance was 57.9% (11/19), while it was 0 in patients without TKI treatment. Among patients with T790M mutation, 1 case had a mutation abundance < 0.1%, 7 cases had a mutation abundance of 0.1%-2.0%, 3 cases had a mutation abundance > 2.0%.Conclusions:The ddPCR provides a non-invasive, highly sensitive and absolutely quantitative method for detecting EGFR mutations in peripheral blood ctDNA of NSCLC patients. It provides a new detection method for EGFR-TKI targeted therapy in NSCLC patients with difficult sampling or with acquired drug resistance who need to repeatedly sample. The approach provides an important basis for the individualized targeted therapy.