Co-mutation features in treatment-naïve EGFR-mutant lung adenocarcinoma.

Abstract

e21616 Background: In Chinese patients with lung adenocarcinoma, the positive rate of EGFR mutation was 40% - 50%, EGFR-TKIs therapy for lung cancer was also aimed at this part of patients. However, different EGFR mutation types have different therapeutic effects, this study focuses on different EGFR mutation types to divide the population of lung adenocarcinoma. Methods: We retrospectively reviewed gene test results of two hundred and sixty-two treatment-naïve adenocarcinoma patients. Tumor tissues (199, 76%), plasma (46, 17.5%) and other samples (17, 6.5%) were subject to next-generation sequencing using a 59-gene panel, which enables simultaneously assess SNV, Indel, rearrangements and CNV variations. Results: There were 174 females. These patients were divided into four groups, which 139 were EGFR L858R, 99 were EGFR exon 19 deletion, 7 were EGFR 20 ins and 17 were uncommon EGFR mutations, the co-mutation proportions with EGFR were 84.9% (118/139), 76.8% (76/99), 71.4% (5/7) and 94.1% (16/17) respectively. The mean numbers of co-mutation genes in L858R and exon 19 deletion were 4.173 and 3.258 (p<0.05). TP53 mutation was detected in 14.3% (1/7) 20ins group, which had a significant difference to L858R (59.7%, 83/139) and uncommon mutation groups (70.6%, 12/17) (p<0.05). Meanwhile, EGFR amplification proportion in L858R (18%, 25/139) and exon 19 deletion (6.1%, 6/99) were significantly different (p<0.05). The actionable mutations associated with target therapy involved in multiple pathways, for example, the HRR pathway and cell cycle pathway, related genes had no significant difference among the four groups. In these lung adenocarcinoma patients, we also found 6 EGFR T790M (2.3%, 6/262). Three cases accompanied with exon 19 deletion, and another three were L858R, no distribution in 20ins and uncommon groups. Conclusions: The phenomenon of concurrent gene mutation in treatment-naïve EGFR-mutant lung adenocarcinoma is common. EGFR mutant subgroups have different co-mutation features, like gene number and mutated genes. It may be the factor leading to different therapeutic effects of EGFR-TKIs, and indicate the importance of multiplex molecular test and further researches of target therapies.