FDG and FAPI PET-based response evaluation to reduced-dose nivolumab in pleural mesothelioma: A case report.

Reliable tools for objective response assessment are essential in pleural mesothelioma treated with immunotherapy. We report on a 75-year-old man with sarcomatoid pleural mesothelioma who received a reduced nivolumab dose after developing a hypersensitivity reaction during the first infusion. CT, [F]FDG PET/CT and [Ga]Ga-Fibroblast activation protein inhibitor-46 (FAPI) PET/CT were performed before and after treatment. Despite the reduced dose, the patient experienced clear clinical benefit, and follow-up imaging demonstrated substantial morphological and metabolic improvement across all imaging modalities. This case offers an unique opportunity to directly compare response assessment across three complimentary imaging modalities.