Sodium Levels and Outcomes in Patients With Metastatic Renal Cell Carcinoma Receiving Nivolumab.

Importance: Low sodium levels have been associated with negative outcomes among patients with metastatic renal cell carcinoma (mRCC) receiving therapies other than immune checkpoint inhibitors (ICIs). Objective: To investigate the role of natremia in patients with mRCC receiving nivolumab as a second-line or subsequent therapy. Design, Setting, and Participants: In this retrospective cohort study, the clinical and biochemical data of patients with mRCC receiving nivolumab were collected from October 2015 to November 2019 as part of a multicenter Italian study. Data analysis was performed from February to March 2023. Exposure: Nivolumab was administered intravenously at a dose of 3 mg/kg every 2 weeks and, since May 2018, at a fixed dose of 240 mg every 2 weeks or 480 mg every 4 weeks. Patients were divided into 2 groups according to their median serum sodium value (<140 or ≥140 mEq/L). Main Outcomes and Measures: The primary outcomes were the associations of pre-ICI and post-ICI sodium levels with overall survival (OS), progression-free survival (PFS), objective response rate, and disease control rate (DCR). The Kaplan-Meier method was used to estimate PFS and OS, and differences between groups were compared using the log-rank test. Results: A total of 401 patients with mRCC receiving nivolumab as second-line therapy were evaluated, and 355 eligible patients (median [range] age, 76 [44-84] years; 258 male patients [72.7%]) were included in the final cohort. Among patients with pre-ICI sodium greater than or equal to 140 mEq/L compared with those with sodium less than 140 mEq/L, the median PFS was 9.3 months (95% CI, 6.5-11.5 months) vs 7.4 months (95% CI, 4.6-10.1 months; P = .90), and the median OS was 29.2 months (95% CI, 21.8-35.9 months) vs 20.0 months (95% CI, 14.1-26.8 months; P = .03). Patients with post-ICI sodium values greater than or equal to 140 mEq/L had longer PFS (11.1 months [95% CI, 8.5-1.5 months] vs 5.1 months [95% CI, 4.1-7.5 months]; P = .01) and OS (32.9 months [95% CI, 25.1-42.6 months] vs 17.1 months [95% CI, 12.6-24.5 months]; P = .006) compared with patients with sodium values less than 140 mEq/L. Patients with both pre-ICI and post-ICI sodium values greater than or equal to 140 mEq/L exhibited a significant improvement in clinical outcomes compared with those with a value less than 140 mEq/L (PFS, 11.5 months [95% CI, 8.8-16.4 months] vs 5.8 months [95% CI, 4.4-8.3 months]; P = .008); OS, 37.6 months [95% CI, 29.0-49.9 months] vs 19.4 months [95% CI, 14.1-24.5 months]; P = .01). Moreover, sodium levels greater than or equal to 140 mEq/L were associated with significantly better DCR than lower sodium levels. Conclusions and Relevance: In this retrospective cohort study of patients with mRCC receiving nivolumab, sodium values greater than or equal to 140 mEq/L, both before and/or after ICI, were associated with better OS and PFS, as well as a higher DCR, compared with levels less than 140 mEq/L. These findings suggest that sodium levels may be associated with survival outcomes in patients with mRCC and may have potential use as variables to consider in patients' risk scores.