Sarcoidosis-Like Reactions Induced by Checkpoint Inhibitors

Immune checkpoint inhibitors (ICIs) are a newly developed component of cancer care that expands the treatment possibilities for patients. Their use has been associated with several immune-related adverse events, including ICI-induced sarcoidosis-like reactions. This article reviews the data concerning ICI-induced sarcoidosis-like reactions currently available in the medical literature. These reactions have been reported in three classes of ICIs: anti-cytotoxic T-lymphocyte associated protein 4 antibodies, programmed death 1 inhibitors and programmed death ligand 1 inhibitors. These reactions are indistinguishable from sarcoidosis with a similar histology, pattern of organ involvement, and pattern of clinical manifestations. The most common locations to observe granulomatous inflammation from these reactions is in intrathoracic locations (the lung and/or mediastinal lymph nodes) and the skin. The median time between initiation of an ICI and the development of a sarcoidosis-like reaction averaged 14 weeks. Clinicians have opted to use corticosteroids and/or discontinue the ICI, or take no action when these reactions have developed. Regardless of whether the clinician performed an intervention or not, these reactions have uniformly improved or resolved after ICI-treatment, which provides additional temporal evidence supporting the presence of a sarcoidosis-like reaction as opposed to sarcoidosis. There is even evidence that the development of an ICI-induced sarcoidosis-like reaction suggests that the ICI is effective as an anti-tumor agent and should be continued. As is the case for sarcoidosis, sarcoidosis-like reactions do not mandate antisarcoidosis therapy, especially if the condition is asymptomatic. When treatment of sarcoidosis-like reaction is required, it may be prudent to continue ICI therapy and add antisarcoidosis therapy because standard antisarcoidosis regimens seem to be effective. Further research into the mechanisms involved in the development of ICI-induced sarcoidosis-like reactions may give insights into the immunopathogenesis of sarcoidosis.