Lung Toxicity from Immune Checkpoint Inhibitors: A Diagnostic Approach

The use of immune checkpoint inhibitors (ICIs) has increased exponentially in recent years, leading to a significant impact on cancer patient survival. However, their administration can trigger immune-mediated adverse effects, notably pulmonary toxicity, which is a potentially serious complication. ICI-induced pneumonitis has a variable incidence ranging from 5 to 19% and usually appears in the first few months of treatment. The diagnosis requires a high index of suspicion, especially in patients with risk factors (elderly male smokers with squamous cell lung cancer, previous respiratory or autoimmune disease, and receiving combination treatment with other ICIs or chemo-radiotherapy). Chest computed tomography (CT) is a key test, allowing the identification of different radiological patterns. This study can be completed with bronchoscopy with bronchoalveolar lavage (BAL) to rule out infection or tumour progression. In general terms, treatment is based on discontinuing the causative drug, with or without the initiation of systemic corticosteroids, escalating to immunosuppressants depending on the severity and/or refractoriness of the condition. This paper provides an updated narrative review of ICI pulmonary toxicity, addressing its pathophysiology, different types of lung damage, diagnostic and therapeutic algorithms, and the emerging role of biomarkers such as KL-6 or IL-6. This article emphasises the need for a multidisciplinary approach and further prospective studies to optimise the management and prognosis of this immune-mediated complication.