Association of Ion Concentration with Immune-Related Adverse Events and Prognosis in Lung Cancer Patients Treated with PD-1/PD-L1 Inhibitors

<b>Objectives</b>: irAEs were associated with immunotherapy response in cancer treatment, but severe irAEs discontinued immunotherapy and affected the quality of life. This study aimed to identify ion concentrations as potential biomarkers for irAEs and prognosis in lung cancer patients receiving ICI therapy. <b>Methods:</b> A retrospective analysis was conducted on 459 lung cancer patients who received ICI treatment at Xiangya Hospital from April 2019 to May 2023. Patient characteristics, ion concentrations (K⁺, Na⁺, Cl^-, Ca²⁺, PO₄ ^3- and Mg²⁺), irAEs, and prognosis were systematically collected. Univariable and multivariable regression analyses, including binary logistic regression and Cox regression models, were employed to identify factors associated with irAEs and PFS. <b>Results:</b> Among 459 lung cancer patients receiving ICI treatment, 378 (82.4%) of the patients suffered irAEs. PD-L1 expression, ICI cycles, ORR and DCR were linked to irAEs occurrence. Cardiotoxicity, hypothyroidism, and dermatoxicity were the predominant irAEs types, but mostly mild to moderate. Notably, elevated potassium (K⁺) level was significantly correlated with both a higher risk of irAEs and longer PFS. <b>Conclusions:</b> The findings suggest that K⁺ concentration prior to initiating treatment with ICIs may be a biomarker of irAEs and PFS in lung cancer patients.