Objective G719 X is the most frequently seen uncommon mutation of the epidermal growth factor receptor（EGFR） gene, which is a point mutation at exon 18 with three common subtypes, G719 A/G719 C/G719 S. This study explored the clinicopathological characteristics of the G719 X mutation and investigated the efficacy of EGFR-tyrosine kinase inhibitor（TKI） treatment and chemotherapy in patients with the G719 X mutation; the survival rate after these different treatment modalities were then analyzed in order to provide evidence for clinical treatment.Methods Clinical data of 41 patients with the G719 X mutation admitted in the Beijing Chest Hospital, Capital Medical University from September 2014 to July 2018, were collected and the EGFR mutations were detected by amplification refractory mutation system-polymerase chain reaction（ARMS-PCR）. The clinicopathological characteristics of the G719 X mutation were analyzed, and the relationship among the G719 X mutation, the efficacy of different treatment modalities, and the progression-free survival（PFS） was analyzed. Results Of the 41 cases, 24（58.5%） were G719 X single mutations and 17（41.5%） were compound mutations, including G719 X/S768 I, G719 X/L861 Q, G719 X/19 del, and G719 X/c-Met compound mutation. The objective response rate（ORR） of first-line EGFR-TKI therapy was 50%（6/12）, the disease control rate（DCR） was 83.3%（10/12）, and the median PFS（mPFS） was 9 months. After resistance to EGFR-TKI in the previous treatment, the ORR（71.4%, 5/7） and DCR（100%, 7/7） were still high following EGFR-TKIs, by an mPFS of 8 months. The ORR of chemotherapy was 33.3%（2/6）, the DCR was 100%（6/6）, and the mPFS was 6 months. Conclusion G719 X is an uncommon mutation of the EGFR gene and is sensitive to many EGFR-TKIs. It can be treated with the second-or third-generation EGFR-TKIs after resistance to the first-generation EGFR-TKIs. G719 X mutation also showed favorable effect to chemotherapy.
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