Ga-68 FAPI PET Before Immunotherapy

This study uses a special type of PET scan (called FAPI PET) to image patients with pleural mesothelioma — a cancer of the lining around the lungs — before they start immunotherapy. The goal is to see whether this scan can predict who will respond better to immunotherapy. **You may be eligible if...** - You have been diagnosed with pleural mesothelioma confirmed by biopsy - You are scheduled to receive immunotherapy (anti-PD-L1 and/or anti-CTLA-4 antibodies) as your first or second treatment - You are in reasonably good health (not severely limited by your illness) **You may NOT be eligible if...** - Your illness severely limits your daily activities (ECOG score above 2) - You are unwilling to provide informed consent Talk to your doctor to see if this trial is right for you.