[Expert consensus on assessing tumor response to immune checkpoint inhibitors by PET/CT (2020 Edition)].

The Immune checkpoint inhibitors (ICIs) have represented a major breakthrough in the field of malignant tumor treatment. However, due to the mechanism of this novel therapy, some special forms of response modes, such as pseudoprogression and hyperprogression, have arisen, which bring difficulties and challenges to the therapeutic efficacy evaluation. In 2017, the European association of nuclear medicine reported the advantages of using 18-fluoro-2-deoxy-D-glucose ((18)F-FDG) PET/CT to evaluate the tumor immunotherapy response and immune-related side effects based on the published clinical trial data. In China, a large amount of research data has been generated since the clinical study of immune checkpoint inhibitors officially started in 2013.Therefore, how to utilize PET/CT reasonably and standardly in tumor immunotherapy has become an urgent clinical and scientific issue. Focusing on the practical questions of examination procedures, PET/CT image interpretation and the evaluation criteria after ICIs treatment, this consensus has been finally formed, which based on the combination of literature, expert experiences, and internal discussion among committee members in the PET Group of Chinese Society of Nuclear Medicine.This consensus is also expected to improve the guide for standardizing the application of PET/CT to evaluate tumor immunotherapy response and promoting the technology in corresponding field.