The Role of PET/CT in the Era of Immune Checkpoint Inhibitors: State of Art.

BACKGROUND: Immune checkpoint inhibitors (ICI) have achieved astonishing results and improved overall survival (OS) in several types of malignancies, including advanced melanoma. However, due to a peculiar type of anti-cancer activity provided by these drugs, the response patterns during ICI treatment are completely different from that with "old" chemotherapeutic agents.
OBJECTIVE: To provide an overview of the available literature and potentials of 18F-FDG PET/CT in advanced melanoma during the course of therapy with ICI in the context of treatment response evaluation.
METHOD: Morphologic criteria, expressed by Response Evaluation Criteria in Solid Tumors (RECIST), immune-related response criteria (irRC), irRECIST, and, more recently, immune-RECIST (iRECIST), along with response criteria based on the metabolic parameters with 18F-Fluorodeoxyglucose (18FFDG), have been explored.
RESULTS: To overcome the limits of traditional response criteria, new metabolic response criteria have been introduced on time and are being continuously updated, such as the PET/CT Criteria for the early prediction of Response to Immune checkpoint inhibitor Therapy (PECRIT), the PET Response Evaluation Criteria for Immunotherapy (PERCIMT), and "immunotherapy-modified" PET Response Criteria in Solid Tumors (imPERCIST). The introduction of new PET radiotracers, based on monoclonal antibodies combined with radioactive elements ("immune-PET"), are of great interest.
CONCLUSION: Although the role of 18F-FDG PET/CT in malignant melanoma has been widely validated for detecting distant metastases and recurrences, evidences in course of ICI are still scarce and larger multicenter clinical trials are needed. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.