Pretreatment serum sodium as a prognostic factor for patients with advanced esophageal cancer receiving immunotherapy or immunotherapy combined with radiotherapy.

e16027 Background: Existing studies have shown that pretreatment serum sodium levels are associated with the prognosis of various cancers. However, the relationship between pretreatment serum sodium levels and prognosis in patients with advanced esophageal cancer (EC) receiving immunotherapy or immunotherapy combined with radiotherapy has not been well elucidated. Methods: We investigated the value of serum sodium levels before immunotherapy or immunotherapy combined with radiotherapy in the prognosis of patients with advanced esophageal cancer. A retrospective analysis was conducted on the data of esophageal cancer patients who received immunotherapy or immunotherapy combined with radiotherapy at a single cancer center. Patients were divided into a low serum sodium group and a high serum sodium group based on the median serum sodium level before treatment. Overall survival (OS) and the 5-year progression-free survival (PFS) were analyzed by using Kaplan-Meier method and Cox regression. Results: In our pre-analysis, the PFS and OS of patients in the low-sodium group were lower than those in the high-sodium group (p < 0.05). A similar association between PFS/OS and sodium levels was observed in the treatment subgroups. Conclusions: The pre-treatment blood sodium level can be used as a serum biomarker to predict the prognosis of patients with advanced esophageal cancer who receive immunotherapy or immunotherapy combined with radiotherapy.