The purpose of this study to learn more about whether the study drug osimertinib (TAGRISSOTM) is more effective than placebo in participants with epidermal growth factor receptor (EGFR) mutated stage IA2 or IA3 Non-Small Cell Lung Cancer (NSCLC) after complete surgical removal of the tumor. Stages IA2 and IA3 refer to tumor size. A placebo is an inactive substance or other intervention that looks the same as, and is given the same way as, an active drug or treatment being tested. The effects of the active drug or other intervention are compared to the effects of the placebo. We are also...