PFS is defined as time from randomisation until progression per RECIST 1.1 as assessed by BICR, or death due to any cause (in the absence of progression).

DFS is defined as the time from the date of randomisation until the date of disease recurrence or date of death (by any cause in the absence of recurrence), whichever occurs first. Stratification to the high risk stratum will be based on pathologic features assessed by central pathology review during screening.

Defined as ≤10% viable cancer cells in the surgical specimen, as assessed per central pathology laboratory post-surgery (IASLC method). Patients will only be considered to have an MPR if they also have an R0 margin result.

Defined as ≤10% viable cancer cells in the surgical specimen, as assessed per central pathology laboratory post-surgery (chemotherapy method). Patients will only be considered to have an MPR if they also have an R0 margin result.

Adverse events were summarized by maximum reported Common Terminology Criteria for Adverse Event (CTCAE) grade, version 5.0. Grade 1 (Mild): asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated. Grade 2 (Moderate): minimal, local or noninvasive intervention indicated; limiting age-appropriate instrumental activities of daily living. Grade 3 (Severe or medically significant but not immediately life-threatening): hospitalization or prolongation of hospitalization indicated; disabling; limiting self-care activities of daily living. Grade 4 (Life-threatening consequences): urgent intervention indicated. Grade 5: Death related to AE. Includes adverse events with onset date on or after the date of first dose and up to and including 28 days following discontinuation of treatment but prior to the start of a new anti-cancer therapy.

Progression-free survival (PFS) using Investigator assessment as defined by RECIST 1.1. Median progression free survival (months) calculated using the Kaplan-Meier method. Progression-free survival (PFS) is defined as the time from randomization until the date of objective disease progression or death (by any cause in the absence of progression), regardless of whether the patient withdraws from randomized therapy or receives another anti-cancer therapy prior to progression. Patients who have not progressed or died at the time of analysis will be censored at the time of the latest date of assessment from their last evaluable RECIST assessment. The primary efficacy analysis of the investigator-assessed progression-free survival will be performed when approximately 278 PFS events and at least 16 months of follow-up after Last subject in, has occurred in the 556 randomized patients.

Sensitivity analysis for progression-free survival (PFS) by blinded independent central review (BICR) using Investigator assessment as defined by RECIST 1.1. Median progression free survival (months) calculated using the Kaplan-Meier method. Progression-free survival (PFS) is defined as the time from randomization until the date of objective disease progression or death (by any cause in the absence of progression), regardless of whether the patient withdraws from randomized therapy or receives another anti-cancer therapy prior to progression. Patients who have not progressed or died at the time of analysis will be censored at the time of the latest date of assessment from their last evaluable RECIST assessment. The primary efficacy analysis of the investigator-assessed progression-free survival will be performed when approximately 278 PFS events and at least 16 months of follow-up after Last subject in, has occurred in the 556 randomized patients.

DFS is defined as the time from the first dosing of study treatment until the date of disease recurrence by investigator assessment or death by any cause in the absence of disease recurrence. DFS rate at 3 years is defined as the proportion of patients alive and disease free at 3 years from the first dosing of study treatment as estimated by Kaplan-Meier method, respectively. Patients who are disease-free and alive at the time of analysis will be censored at the date of their latest follow-up assessment known to be disease-free

Percentage of evaluable patients with an Investigator-assessed visit response of complete response (CR) or partial response (PR). CR defined as disappearance of all target and non-target lesions and no new lesions. PR defined as \>= 30% decrease in the sum of diameters of target lesions (compared to baseline) and no new non-target lesions. Overall Response (OR) = CR + PR.

Per Response Evaluation Criteria in Solid Tumours (RECIST v1.1) assessed by MRI or CT: Complete Response (CR): Disappearance of all target and non-target lesions and no new lesions; Partial Response (PR): \>= 30% decrease in the sum of diameters of Target Lesions (compared to baseline) and no new lesions. ORR is the percentage of patients with at least 1 visit response of CR or PR (according to independent review) that was confirmed at least 4 weeks later, prior to progression or further anti-cancer therapy.

During the PET examination time, a series of arterial blood samples were taken to measure Cmax, %ID brain of \[11C\]osimertinib.

During the PET examination time, a series of arterial blood samples were taken to measure Cmax, SUV brain of \[11C\]osimertinib.

The Tmax, brain was determined directly from the observed concentration versus time data.

The Kp was defined as ratio of radiolabeled drug in brain to that in plasma calculated as area under the brain radioactivity concentration-time curve between 0 and 90 minutes/area under the plasma radioactivity concentration-time curve between 0 and 90 minutes.