Atypical Response Patterns and Immune-related Adverse Events Detected by FDG PET/CT in Patients Receiving Immunotherapy: A Case Series and Literature Review

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy, yet their efficacy assessments using conventional imaging remain challenging due to atypical response patterns and immune-related adverse events (irAEs). We present a case series of five patients who underwent different immunotherapies for various solid cancers and were evaluated with 18F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT), highlighting pseudoprogression, dissociated responses, sarcoid-like reactions, and immune-mediated pancreatitis. This series underscores the pivotal role of PET/CT in distinguishing between true progression, treatment-related inflammatory changes, and emphasizes the need for physicians to be aware of these phenomena.