EGFR delE709_T710insD

This specific mutation in exon 18 seems to respond to certain EGFR TKIs such as afatinib. However, given the rarity of this mutation, determining the most effective TKI for its treatment remains unclear. We report a 70-year-old woman diagnosed with stage IV-A lung adenocarcinoma harboring EGFR delE709_T710insD mutation treated in first-line with Osimertinib using standard schedule and doses experiencing renal toxicity and disease progression after 9 weeks of treatment.

When EGFR mutation is suspected, complete DNA sequencing of exons 18 to 21 should be carried out and we suggest that afatinib should be the first-line treatment for exon 18 delE709_T710insD-mutated advanced lung adenocarcinomas. Rare EGFR gene mutations are not detected by standard diagnostic kits.DNA sequencing is required to diagnose rare mutations of the EGFR gene.delE709_T710insD-mutated stage IV lung adenocarcinomas respond to afatinib.

Loperamide prophylaxis (first 8 weeks) was mandatory. Meaningful neratinib activity, regardless of single or complex G719X mutation, was seen in TKI-pretreated NSCLC patients with EGFR exon 18 mutations. ORR and mPFS appear better than previously reported for other EGFR TKIs in TKIrefractory patients. The neratinib SUMMIT trial continues to enroll EGFR exon 18-mutant NSCLC patients.