Fractional exhaled nitric oxide in checkpoint inhibitor pneumonitis: a case report and literature review

Plain language summaryWe report a patient with advanced lung cancer who experienced shortness of breath induced by immunotherapy. The levels of nitric oxide from the exhaled breath in this case showed obvious increases. Currently, monitoring systems for treatment-related lung injury remain elusive. This is the first report highlighting the potential value of measuring nitric oxide from the exhaled breath to screen for airway inflammation in patients receiving immunotherapy. The dynamic changes of the levels of nitric oxide from the exhaled breath may be correlated with the development of airway inflammation during immunotherapy. Checkpoint inhibitor pneumonitis (CIP) is a relatively rare adverse event and a potential cause of death in patients treated with immune checkpoint inhibitors (ICIs). Because the symptoms and signs are nonspecific, the diagnosis of CIP is challenging. Additionally, compared with the biomarkers that can monitor the effect of ICIs, there is less research evaluating markers to monitor CIP. We report a case of CIP induced by camrelizumab in a patient with advanced non-small-cell lung cancer, in which the fractional exhaled nitric oxide levels showed obvious increases. Fractional exhaled nitric oxide may have the potential to monitor the condition of airway inflammation in patients using ICIs.