Next-generation sequencing of tissue and circulating tumor DNA: Resistance mechanisms to EGFR targeted therapy in a cohort of patients with advanced non-small cell lung cancer

Background: Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) has been considered as an effective treatment in epidermal growth factor receptor-mutant (EGFR-mutant) advanced non-small cell lung cancer (NSCLC). However, most patients develop acquired resistance eventually. Here, we compared and analyzed the genetic alterations between tissue assay and circulating tumor DNA (ctDNA), and further explored the resistance mechanisms after EGFR-TKI treatment. Methods Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), Cobas® ARMS-PCR and next-generation sequencing (NGS) were performed on tissue samples after pathological diagnosis. Digital droplet PCR (ddPCR) and NGS were performed on plasma samples. The association between genetic alterations and clinical outcomes was analyzed retrospectively. Results Thirty-seven patients were included. The success rate of re-biopsy was 91.89% (34/37). The total detection rate of EGFR T790M was 62.16% (23/37) and the consistency between tissue and ctDNA was 78.26% (18/23). Thirty-four patients were analyzed retrospectively. Twenty-four patients harbored concomitant mutations. Moreover, tissue re-biopsy at resistance showed 21 patients (21/34, 61.76%) had concomitant T790M mutation, 4 with MET amplification and 4 with PIK3CA mutation. Patients with T790M mutation ( p  = 0.010 & p  = 0.017) or third-generation EGFR-TKI treatment ( p  < 0.0001 & p  = 0.073) showed better progression-free survival (PFS) and overall survival (OS). Interestingly, concomitant genetic alterations were significantly associated with a worse prognosis for patients with T790M mutation receiving third-generation EGFR-TKIs ( p  = 0.037). Conclusions Multi-platforms are feasible and highly consistent for re-biopsy after EGFR-TKI resistance. Concomitant genetic alterations may be associated with a poor prognosis for patients with T790M mutation after third-generation EGFR-TKIs. Trial Registration: The clinical trial registration was carried out on ClinicalTrials.gov. (NCT03309462), registered on September 1st 2017. https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S0007G1B&selectaction=Edit&uid=U0001WUU&ts=2&cx=frpicv