The Importance of Imaging Studies in the Assessment of Response to Immunotherapy in Lung Cancer

Immunotherapy (particularly immune checkpoint inhibitors) in the treatment of patients with lung cancer has aroused great interest in recent years, revolutionized the management of patients with locally advanced/metastatic disease, and given hope to both patients and treating physicians. These drugs, in combination or in monotherapy, have become the standard treatment for many patients with lung cancer, and their use is expected to increase significantly in the near future. In this article, we will review the growing importance of imaging techniques in the evaluation of therapeutic response to immunotherapy in lung cancer patients, with emphasis on the new specific radiological criteria on response to immunotherapy, atypical radiological responses (pseudoprogresion, dissociative responses, hyperprogresion), and the main radiological manifestations of adverse events associated with immunotherapy (sarcoid reactions, pulmonary toxicities, etc.). Pulmonologists must be familiar not only with atypical radiological responses to immunotherapy and their prognostic implications, but also with their effects and the new radiological criteria of response to assess treatment response. In this study, we will address key concepts such as "pseudoprogresion", "paradoxical response", "hyperprogresion", or "unconfirmed progression", and their significance in the management of patients with lung cancer treated with immunotherapy.