Late Breaking Abstract - Role of exhaled nitric oxide in predicting checkpoint inhibitor-related pneumonia：prospective observational study

<bold>Background and Objective:</bold> Checkpoint inhibitor-related pneumonia (CIP) is one of the most fatal complications of immune checkpoint inhibitors (ICIs). There is still a lack of effective biomarkers to predict CIP. Exhaled nitric oxide (eNO) concentrations can be measured by non-invasive devices, but its value in CIP is unknown. We aimed to investigate the value of eNO in CIP. <bold>Methods:</bold> eNOs at exhalation flow rates of 50 and 200ml/s（FeNO₅₀和FeNO₂₀₀）were measured in cancer patients who received ICIs, and they were divided into CIP group and non-CIP group. CaNO was calculated based on a two-compartment model. Medical records of patient were collected. The receiver operating characteristic (ROC) curve was used to determine the optimal CaNO cut-off value. <bold>Results:</bold> 81 patients completed eNO testing, including 29 patients with CIP (34.5%). CaNO and FeNO₅₀ was significantly increased in CIP group (6.8±4.2ppb vs 3.8±3.1ppb, p=0.001) and (18.4±13.0ppb vs 27.7±19.5ppb, p=0.021). There was no significant difference in FeNO₂₀₀ (10.4±3.9ppb vs 9.4±4.7ppb, p=0.1592). The area under ROC curve of CaNO to predict CIP was 0.714 (95%CI: 0.952-0.837, p=0.001). The best cut-off value of CaNO was 6.4 ppb. Multivariate analysis showed that chest radiotherapy (OR=13.055; 95%CI 2.892-94.377; p=0.037), CaNO (OR=1.238, 95%CI 1.072-1.460, p=0.010) and FeNO₅₀ (OR=0.965, 95%CI 0.923-1.001, p=0.080)were independently associated with a higher incidence of CIP. <bold>Conclusions:</bold> CaNO may become a new marker for predicting CIP. Increased CaNO, lower FeNO₅₀ and chest radiotherapy identifies CIP and may help to initiate early appropriate treatment.