Abstract
Afatinib exhibits therapeutic efficacy for lung adenocarcinoma patients harboring HER2 exon 20 insertions. HER2 S310Y single site substitution was discovered in recent years and afatinib efficacy for adenocarcinoma patients harboring S310Y mutation has not been reported. We presented a case of a 41-year-old male patient with lung adenocarcinoma harboring the HER2 S310Y mutation obtained clinical response to the treatment of afatinib, an oral HER family blocker. After the treatment of afatinib, the patient achieved partial response (PR) in chest lesions and almost complete response (CR) in intracranial lesions. He experienced progressive disease (PD) with liver metastasis and achieved a progression-free survival (PFS) of 5 months. He continually treated with afatinib after CT guided percutaneous radiofrequency ablation to eradicate the hepatic tumor cells and achieved stable disease (SD). In this study, we reported the first clinical evidence of efficacy generated by afatinib, the irreversible HER family inhibitor, targeting HER2 S310Y single site mutation in lung adenocarcinoma.