This clinical trial is focused on studying a type of lung cancer known as Non-Small Cell Lung Cancer (NSCLC) that can be surgically removed. The study is specifically for patients whose cancer has a mutation in the Epidermal Growth Factor Receptor (EGFR), which is a protein that can affect how cancer cells grow. The trial will explore the effectiveness of a medication called Osimertinib, also known by its code name AZD9291, used alone or in combination with chemotherapy, compared to chemotherapy alone. Chemotherapy drugs used in this study include Cisplatin, Carboplatin, and Pemetrexed. A placebo, which looks like the real medication but has no active ingredients, may also be used in some cases.

The purpose of the study is to determine how well Osimertinib works as a treatment before surgery, either by itself or with chemotherapy, compared to just using chemotherapy. Participants will receive treatment over a period of time, and their response to the treatment will be monitored. The study will involve taking the medication in the form of tablets or through an intravenous infusion, which means the medication is given directly into a vein.

Throughout the study, the main focus will be on how the cancer responds to the treatment, particularly looking at the number of cancer cells remaining after treatment. Other aspects, such as the overall survival of participants and any changes in their quality of life, will also be observed. The study aims to provide valuable information on the best treatment approach for patients with this specific type of lung cancer.