The Impact of Sodium on Prognosis in RCC and NSCLC Patients Receiving Second-line Nivolumab Treatment

Objective: This study aimed to explore whether serum sodium concentrations could serve as a prognostic marker in patients with metastatic renal cell carcinoma (mRCC) and metastatic non-small cell lung cancer (mNSCLC) who were treated with nivolumab in the second-line setting. Material and Methods:In this retrospective analysis, demographic, clinical, and pathological information on patients with mRCC or mNSCLC who were treated with second-line nivolumab was reviewed.Serum sodium levels were measured at baseline and at week 4 after treatment initiation, and survival outcomes were analyzed.The diagnostic impact of the sodium level was assessed with regression analyses.Results: A total of 99 patients were included in the study: 18 with mRCC and 81 with mNSCLC.In mNSCLC, the median overall survival (mOS) for cohort members with pre-immune checkpoint inhibitors (ICI) sodium (Na) <140 (serum sodium measured within approximately 5 days of ICI initiation) was 6.5 months, compared with 12.2 months for those with pre-ICI Na 140 (p=0.049).Among patients with mNSCLC, the mOS of patients with post-ICI Na <140 (week-4 serum sodium values after ICI initiation) was 6.8 months, whereas that of patients with post-ICI Na 140 was 16.8 months (p=0.313).In mRCC, the median OS among patients with a pre-ICI Na <140 was 25.7 months, compared with 20.8 months for those with a pre-ICI Na 140 (p=0.514).In mRCC, the mOS of patients with post-ICI Na <140 was 12.7 months, whereas in those with post-ICI Na 140, the median was not reached (p=0.457).In multivariate Cox regression analysis, baseline serum sodium emerged as an independent predictor of OS in the mNSCLC cohort, underscoring its potential as a clinically relevant prognostic biomarker. Conclusion:Baseline sodium levels appear to predict prognosis in mNSCLC, whereas this association was not evident in mRCC.In particular, pretreatment serum sodium demonstrated an independent relationship with OS in the mNSCLC cohort, suggesting its potential utility as a practical and inexpensive prognostic biomarker.More clinical studies are needed to understand the prognostic effects of sodium in patients receiving immunotherapy.