Diclofenac for the Treatment of Patients With Metastatic Non-small Cell Lung Cancer on Single Agent Immunotherapy

This study is testing whether adding diclofenac (a common anti-inflammatory medication) to ongoing immunotherapy can help slow or reverse cancer growth in people with advanced or metastatic non-small cell lung cancer (NSCLC) whose cancer is slowly progressing on a single immunotherapy drug. **You may be eligible if...** - You are 18 or older - You have Stage III or IV non-small cell lung cancer - You are currently receiving a single PD-(L)1 immunotherapy drug (such as pembrolizumab, atezolizumab, nivolumab, or cemiplimab) for at least 12 weeks - Your cancer is showing some signs of progression, but your doctor has decided it is not yet urgent enough to change your treatment **You may NOT be eligible if...** - Your cancer is rapidly progressing and needs immediate treatment change - You have known allergies or contraindications to diclofenac or similar anti-inflammatory drugs - You have serious kidney, liver, or cardiovascular disease - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.