This clinical trial is studying how well diclofenac, a common pain reliever, works in patients with a type of lung cancer called non-small cell lung cancer (NSCLC) that has spread to other parts of the body. Patients are also receiving immunotherapy, a treatment that helps the immune system fight cancer. The study aims to see if taking diclofenac can help stop the cancer from growing by reducing inflammation and improving the effectiveness of the immunotherapy.

Key Points:

• Participants will take diclofenac pills twice daily along with their current immunotherapy every 21 or 28 days.
• They will need to visit the clinic for regular check-ups, blood tests, and scans.
• After the study treatment, follow-up visits will occur every 12 weeks for up to a year.

Participants must be at least 18 years old and on certain immunotherapy drugs for at least 12 weeks. They should be able to take oral medications and have a life expectancy of at least 26 weeks. Certain health conditions, medications, and other factors might disqualify someone from participating.