The efficacy of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in lung squamous cell carcinoma is said to be low. Thus far, only four cases of osimertinib in lung squamous cell carcinoma have been published. We experienced a case of EGFR mutant lung squamous cell carcinoma in which fifth-line treatment with osimertinib was effective after T790M EGFR mutation turned positive. Osimertinib was resumed after sixth-line chemotherapy was ineffective, showing efficacy again. Osimertinib may be a promising treatment option for EGFR mutant lung squamous cell carcinoma. This is the first report to show its effect in a case of rechallenge after intervening chemotherapy. It may therefore be important to evaluate EGFR in never-smoker lung squamous cell carcinoma patients.
Keywords: EGFR; TKI; adenosquamous; epidermal growth factor receptor; rechallenge; tyrosine kinase inhibitor.