EGFR mutation types and abundance were associated with the overall survival of advanced lung adenocarcinoma patients receiving first-line tyrosine kinase inhibitors

Background: Epidermal growth factor receptor tyrosine kinases inhibitors (EGFR-TKIs) are currently recognized as the standard treatment for advanced non-small cell lung cancer (NSCLC) patients with EGFR mutations. Clinically found patients with different EGFR mutational status have different prognosis. Methods: A retrospective cohort study was performed to explore the relationship between EGFR mutations and abundance with patient survival by using patient data from the Affiliated Cancer Hospital of Zhengzhou University between January 2013 and November 2016. All patients involved in the present study had sensitive EGFR mutations [either exon 19 deletion (DEL) or exon 21 L858R] and treated by EGFR-TKIs. They were followed up every three months until lost or dead. Mutation abundance was calculated as the copies of EGFR mutation divided by copies of EGFR locus, and the cut-off values for 19DEL and L858R were 4.9% and 9.5%, respectively. Results: Total of 236 patients were included, comprising 116 (49.2%) patients with 19DEL mutation and 120 (50.8%) patients with L858R mutation. The median follow-up duration was 23.2 months (95% CI: 14.9-26.7 months). Overall survival (OS) was significantly longer in patients with 19DEL mutation (20.9 months, 95% CI: 17.7-24.1 months versus 17.0 months, 95% CI: 14.4-19.6 months in patients with L858R; P=0.008) and in patients with high mutation abundance (20.9 months, 95% CI: 18.3-23.5 months versus 13.0 months, 95% CI: 10.3-15.7 months in patients with low mutation abundance; P<0. 001). Multivariate Cox regression including age, performance status and tumor stage revealed that longer OS was independently associated with 19DEL mutation (HR: 0.48, 95% CI: 0.39-0.67, P=0.033) and high mutation abundance (HR: 0.62, 95% CI: 0.50-0.79, P=0.027). Conclusions: EGFR mutation types and abundance was associated with the patients' survival which might be used to predict the efficacy of targeted therapy by EGFR-TKIs.