Radiological manifestations of immune-related adverse effects observed in patients with melanoma undergoing immunotherapy.

Immunotherapy drugs work by stimulating the patient's own immune system to recognize and destroy cancer cells. This subclass of drugs is increasingly administered to patients with advanced melanoma. They are also commonly incorporated into other cancer therapies such as non-small cell lung cancer, renal cancer, head and neck cancers and Hodgkin lymphoma. The most commonly administered immunotherapeutic agents in the treatment of melanoma include programmed cell death protein 1 (PD-1) inhibitors, cytotoxic T-lymphocyte antigen 4 (CTLA-4) inhibitors and a subclass of cytokines. During treatment with these antibodies, a unique set of adverse effects may occur which are often called immune-related adverse events (irAEs). It is vital for radiologists to be aware of and document these side effects during routine staging or body imaging during therapy. Some of these include pneumonitis, colitis, hypophysitis, lymphadenopathy or sarcoid-like syndrome and myositis. IrAEs such as sarcoid-like lymphadenopathy can mimic progression of disease. Serious side effects are seen in less than 10% of patients, and typically emerge between 6 and 12 weeks after commencing treatment. The clinical manifestations of these side effects typically vary from mild to severe and so do the radiological findings. Patients with mild side effects are often treated successfully with systemic corticosteroids, while severe cases require cessation of immunotherapy. We provide a pictorial article on the common irAEs and the associated radiological manifestations.