Vascular FDG Uptake on PET/CT in Patients Receiving Immune Checkpoint Inhibitors

Objective: Numerous drug-related adverse effects are difficult to distinguish because they emerge concurrently with disease progression. Aside from case reports and case reviews, there is a paucity of publications providing detailed analyses of immune checkpoint inhibitors (ICIs) in relation to increased vascular FDG Uptake on positron emission tomography/computed tomography (PET/CT). Material and Methods: The study comprised patients with histopathologically diagnosed cancer who were treated with ICIs. We analysed pre- and post-treatment PET/CT images to calculate the PET vascular activity score (PETVAS) for 15 vascular areas. We specifically examined patients with greater uptake compared with baseline. Patients with non-small cell lung cancer (NSCLC) were categorised based on an increase in uptake; progression-free survival (PFS) and overall survival (OS) were compared. Results: One hundred forty eight patients were included in the study. A total of 482 PET/CT images were examined. Patients received five different ICIs across 13 cancer types. Ten (6.7%) patients exhibited increased 18F-fluorodeoxyglucose (FDG) uptake relative to pretreatment. Two of them (1.3%) had grade 2 or higher uptake. Among 68 NSCLC patients, higher uptake did not significantly affect PFS or OS (p=0.73 for PFS and p=0.37 for OS; both p>0.05). Conclusion: Clinical and biochemical manifestations of underlying malignancy may obscure ICI-related arteritis. In patients presenting with unexplained constitutional symptoms and elevated acute-phase reactants, the PETVAS score may support the identification of clinically relevant vascular FDG uptake and help guide further diagnostic evaluation.