The role of radiology in the evaluation of the immunotherapy efficacy

In the last years, a great interest has arisen on immunotherapy for the treatment of advanced non-small cell lung cancer (NSCLC). Check-point inhibitor drugs are now considered clinical practice standard in different settings and their use is expected to increase significantly in the near future. As treatment options for lung cancer advance and vary, the different patterns of radiological response increase in number and heterogeneity. To correctly evaluate the radiological findings after and during these treatments is of paramount importance, both in the clinical and sperimental setting. In consideration of their peculiar mechanism, immunotherapies can determine unusual response patterns on imaging, that cannot be correctly evaluated with the traditional response criteria such as World Health Organization (WHO) and Response Evaluation Criteria in Solid Tumours (RECIST). Therefore, during these years, several response criteria [immune-related response criteria (irRC), irRECIST and iRECIST] were proposed and applied in clinical trials on immunotherapies. The aim of this review is to describe the radiological findings after immunotherapy, to critically discuss the different response criteria and the imaging of immune-related adverse events.