Neurocognition in NSCLC Patients Treated With Osimertinib or Osimertinib + WBI

Osimertinib at a dose of 80 mg once per day, and WBI

Osimertinib at a dose of 80 mg once per day, until unacceptable adverse events or disease progression occurred. WBI could be given to patients in experimental arm at any time base on investigator's decision after treatment initiated.