Thoracic Imaging of Solid Tumor Patients Treated with Immune Checkpoint Inhibitors

Purpose of Review: Immune checkpoint inhibitors harness the patient’s own immune system to fight cancer. They are now approved for treating a number of solid malignancies, with more agents and indications expected in the coming months and years. Because of their unique mechanism of action, these agents may lead to unusual imaging appearances. Recent Findings: Rare patients may experience pseudoprogression, whereby tumors may initially increase in size or number despite response to therapy. Many patients will experience autoimmune side effects including pneumonitis, which may lead to respiratory compromise and will necessitate cessation of therapy. Occasionally pneumonitis or a sarcoid-like reaction can mimic metastatic disease. Summary: It is imperative that radiologists be aware of these unusual imaging manifestations in patients on immunotherapy so that they are able to assist oncologists in appropriately treating these patients. In particular, we urge caution in interpreting new or enlarging lesions, since these may not always mean progression of disease. Additionally, radiologists should look out for potential immune-related side effects of these therapies. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.