5905 EGFR mutant patients (39.2%, 5905/15078) were identified, with 26 cases (0.44%, 26/5905) harbored EGFR E709-T710delinsD. Afatinib showed a better overall objective response rate (ORR) compared with the first-generation (1G) EGFR TKIs and chemotherapy with significant difference. Superior progression free survival (PFS) was also observed in patients treated with afatinib (afatinib 10.85 m vs 1G EGFR TKIs 4.0 m vs chemotherapy 2.8 m, p = 0.0007)....This is the largest studies for EGFR E709-T710delinsX, with 26 cases with EGFR E709-T710delinsX being identified (0.44% in EGFR mutant NSCLC, 0.17% in NSCLC patients). This study also firstly revealed that afatinib might exert superior antitumor activity to the 1G EGFR TKIs and chemotherapy in EGFR E709-T710delinsX mutant patients.

A 58-year-old Caucasian woman with no smoking history presented with advanced non-small cell lung cancer….In the meantime, the next-generation sequencing results of the liver biopsy had revealed an exon 18 E709_T710delinsD mutation. Therefore, afatinib was administered, which was moderately tolerated with grade 2 paronychia and acneiform skin eruption. After 6 months, a partial response with ongoing decrease of the liver metastasis was retained.