It is aimed to evaluate FAP expression and its success in predicting treatment response before immunotherapy used in the treatment of malignant mesothelioma with Ga68 FAPI PET/CT imaging, which allows in vivo evaluation of FAP expression, which is thought to be associated with immunosuppression and resistance to immunotherapy.

Patients diagnosed with pleural mesothelioma and planned for immunotherapy will be included in the study. Patients will undergo Ga68 FAPI PET/CT imaging within 10 days before the start of immunotherapy treatment, and SUVmax, SUVmean, metabolic tumor volume and total Ga68 FAPI uptake parameters will be obtained from the tumors. Following this, the routine treatment and follow-up of the patients will be carried out by their clinicians. It will be evaluated whether there is a correlation between treatment response and initial Ga-68 FAPI PET findings.

Inclusion Criteria:

• Having a histopathologically confirmed diagnosis of
• Pleural Mesolthelioma
• Patients scheduled for immunotherapy with anti-PDL-1 and/or anti-CTLA-4 antibodies as first or second line therapy
• Patients who gave informed consent form to participate in the study

Exclusion Criteria:

• ECOG>2
• Patients who did not provide informed consent form to participate in the study