Abstract
INTRODUCTION: Immune checkpoint inhibitors have revolutionized the management of many cancers and achieved efficacy and durable response for some patients, including those with advanced cancers. However, immunotherapy is associated with side effects caused by the infiltration of immune cells into normal tissues, which can lead to disproportionate dysimmune reactions. While mostly of moderate intensity, these side effects can affect any organ, including the lung, the site of occasionally life-threatening interstitial lung disease. Their presentation can be similar to that of infectious pneumonia (COVID-19). OBSERVATIONS: We report the cases of 3 patients who presented between March and May 2020 with severe pulmonary toxicities secondary to immunotherapy, which led to with an initial hypothesis of SARS-CoV-2 pneumonia. After extensive investigations, the diagnosis of pulmonary toxicity to immunotherapy was given, and the clinical and radiological course following the initiation of corticosteroid therapy was favorable. CONCLUSION: Pulmonary toxicity secondary to immunotherapy remains a rare but potentially life-threatening side effect. The diagnostic approach requires the elimination of several differential diagnoses (infectious process, tumor progression, other etiologies of interstitial lung disease). This adverse event is reversible and evolution after initiation of corticosteroid therapy is usually favorable.