Facts and Hopes for PET Imaging-Derived Immunotherapy Biomarkers.

Current immunotherapies have brought major progress in cancer treatments, but not all patients benefit. Therefore, insight into reasons for treatment failure and optimal biomarkers for patient selection are warranted. Current approved biomarkers for cancer immunotherapy do not provide insight into characteristics across tumor lesions in a patient or their heterogeneity. Here, whole-body PET imaging with specific tracers may provide support. Moreover, the biodistribution of cell therapies and complex molecules, such as bispecific antibodies, can be visualized by PET imaging, and repeat PET imaging allows to study the whole-body kinetics of the immune response. In this review, we present the status of using PET imaging-derived biomarkers for patients with cancer receiving immunotherapy. Next, the hopes and scientific challenges ahead to optimize current PET imaging biomarker development and to discover novel PET-derived baseline and dynamic biomarkers to potentially guide us in drug development and more precise patient and therapy selection will be discussed.