Neurocognition in NSCLC Patients Treated With Osimertinib or Osimertinib + WBI

Account for patients with wild type EGFR, sample attrition , incidence rate of symptomatic brain metastasis(10%) and any other reasons for screen failure rate(50%), it is esimated that 88 patients will be randomized from 5 sites. Patients will be randomized 1:1, the experimental arm is upfront Osimertinib with WBI sequential therapy, while the control arm is Osimertinib plus 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. Patients will be stratifed at randomization by GPA score (3.5-4 vs \<3.5) and the mutation type (Ex19Del / L858R). Patients will undergo the neurocognition, efficacy and safety assessments at baseline, and every 8 weeks until treatment is completed or discontinued. About time to brain metastases symptoms deterioration, the assessment was repeated in the first week (on site), second week (through telephone) and fourth week (on site). The rest assessment will be as well as other evaluations repeated every 8 weeks. To evaluate the correlation and predictive or prognostic value between gene dynamic changes and clinical efficacy, the tissue, plasma and cerebrospinal fluid (CSF) samples will be collected at baseline. CSF will be collected in patients with intracranial progression. Plasma will be collected in all the patients at disease progression, while tissue is optional. Also, plasma will be collected at week 8(first evaluation of efficacy).