Impact of low sodium values on survival outcomes of patients with cancer receiving immune checkpoint inhibitors.

Background: Low serum sodium affects cancer prognosis, but its impact on immunotherapy is unclear. Objective: Assessing the association of pre- and post-ICI treatment sodium levels with survival. Methods: We retrospectively analyzed patients receiving ICI in January 2012-December 2023, collecting serum sodium levels at treatment initiation and 4 weeks post-ICI, with overall survival (OS) as the primary outcome. Results: Low sodium was observed in 125 and 119 patients pre-and post-treatment respectively. Pre-ICI and post-ICI low sodium correlated with decreased OS [10.6 vs. 22.9 months ( p = 0.001) and 11.6 vs. 27.2 months ( p = 0.009)]. Multivariate analysis identified pre-ICI low sodium [HR: 1.685; 95% CI: 1.050-2.705; p = 0.031] as an independent risk factor for worse OS. Conclusion: Low baseline serum sodium was an independent risk factor for poor OS in patients treated with ICIs.