This clinical trial is focused on studying the treatment of Non-Small Cell Lung Cancer (NSCLC), which is a type of lung cancer that can be surgically removed. The study involves the use of a medication called atezolizumab, which is an immunotherapy drug that helps the immune system fight cancer. Atezolizumab will be used in combination with platinum-based chemotherapy, which includes drugs like cisplatin and carboplatin. These chemotherapy drugs contain platinum and are used to kill cancer cells. The study also involves a placebo, which is a substance with no active medication, to compare the effects of atezolizumab.

The purpose of the study is to evaluate how effective and safe the treatment is when given before surgery (neoadjuvant treatment) and followed by additional atezolizumab after surgery (adjuvant treatment). Participants will receive the treatment through an intravenous infusion, which means the medication is given directly into a vein. The study will last for a period of time, during which participants will receive the treatment and be monitored for any changes in their condition.

Throughout the study, the main focus will be on how long participants remain free from cancer events, which is known as event-free survival. The study will also look at other outcomes, such as the overall survival of participants and any side effects they may experience. The goal is to determine if the combination of atezolizumab and platinum-based chemotherapy is more effective than chemotherapy alone in treating early-stage resectable NSCLC.