Hyponatremia as a prognostic and predictive factor in metastatic renal cell carcinoma

Background: Low serum sodium has recently been associated with poor survival in localised renal cell carcinoma (RCC). We now show the prognostic effect of serum sodium in patients with metastatic RCC (mRCC). Methods: Cohort A comprised 120 consecutive patients with mRCC receiving subcutaneous, low-dose interleukin-2 and interferon-α. Hyponatremia was assessed in univariate and multivariate analyses. An independent cohort of another 120 patients with mRCC was used for validation (cohort B). Results: In cohort A, estimated 5-year survival was 15% and median survival was 15.1 months. Serum sodium ranged between 126 and 144 mM. Twenty-four patients (20%) had serum sodium levels below normal range (1.5 upper normal level (P=0.002), and number of metastatic sites (+3) (P=0.003). In cohort B, serum sodium ranged between 128 and 146 mM. Seventeen patients (14%) had sodium levels below normal range. In multivariate analysis, serum sodium was validated as an independent prognostic factor (P=0.001). A significant association between lack of response and hyponatremia was observed in both cohorts (P=0.003 and P=0.02, respectively). Conclusion: Low serum sodium is a new, validated, independent prognostic, and predictive factor in patients with mRCC.