Rare exon 18 G719A and exon 21 L833V compound EGFR mutations show favorable response to Third-Generation TKI Furmonertinib: A case report and literature review

EGFR exon 19 deletions and exon 21 point mutations are the most common mutations in lung adenocarcinoma, with patients deriving significant clinical benefits from EGFR tyrosine kinase inhibitors (TKIs). However, the efficacy of TKIs in rare compound EGFR mutations remains uncertain. We report a case of lung adenocarcinoma with concurrent EGFR exon 18 G719A and exon 21 L833V mutations, showing a favorable response to third-generation TKI treatment. We reported a case of a 63-year-old female patient with brain, bone, and adrenal metastases from lung adenocarcinoma. Next-generation sequencing analysis identified a rare EGFR exon 18 G719A mutation in combination with an EGFR exon 21 L833V mutation. The patient received furmonertinib as first-line treatment and achieved a sustained response lasting over 12 months. This is the first reported case highlighting the efficacy of a third-generation TKI in treating lung adenocarcinoma with this rare compound mutation. Our findings suggest that third-generation TKIs may be a viable therapeutic option for prolonging progression-free survival in this patient subset.