This study is examining the use of **immunotherapy** for lung cancer, a treatment that uses the body's own immune system to fight cancer cells. The trial focuses on patients with **stage IIIB-IV non-small cell lung cancer (NSCLC)**. The study will look at the effectiveness of first-line treatment using drugs that block proteins PD1 or PD-L1, which help cancer cells evade the immune system. It will also explore second-line treatments for patients whose cancer progresses. A key part of the study is checking **circulating tumor DNA (ctDNA)** in the blood, which can signal changes in cancer status before traditional scans. **Key Points:** - **Study Length and Visits**: Treatment could last up to 24 months with regular blood tests and scans. - **Compensation and Risks**: Details about compensation aren't provided; potential risks include side effects from medications. - **Eligibility**: Participants must be 18 or older with diagnosed stage IIIB or IV NSCLC and need to meet specific health criteria. The goal is to develop personalized treatment plans and improve survival rates by understanding how patients respond to different therapies. Participation involves regular monitoring and multiple treatments, but it could provide valuable insights for future cancer treatments.