Serum-sodium as an independent prognostic factor in metastatic renal cell carcinoma

5102 Background: Recently, low serum sodium has been associated with poor disease-free and overall survival in localized renal cell carcinoma (RCC) (Vasudev, Clin Can Res. 2008). The present study investigated the prognostic impact of serum-sodium values below normal in patients with metastatic RCC (mRCC). Methods: A cohort of 120 consecutive patients with mRCC received subcutaneous, low-dose Interleukin-2 and Interferon-α at Dept. of Oncology, Aarhus University Hospital, from 2002 to 2004 (Cohort A). Baseline variables were collected retrospectively. Follow up was at least 4 years. Potential prognostic factors were analyzed by univariate and multivariate analyses. Endpoint was overall survival. An independent cohort of 120 consecutive patients with mRCC was used for validation. These patients were treated with interleukin-2 based regimens at the same institution from 1999 to 2002 (Cohort B). Data in this cohort were prospectively collected. Results: In cohort A, the estimated 5-year survival rate was 15% and the median survival was 15.1 months. Serum-sodium ranged between 126 and 144 mmol/l. Twenty-four patients (20%) had serum-sodium levels below normal range (7) (HR 1.75, CI 1.1–2.8, p = 0.018), lactate dehydrogenase >1.5 upper normal level (HR 2.09, CI 1.3–3.3, p = 0.002), and number of sites (+3) (HR 1.92; CI 1.3–2.9, p = 0.003). In cohort B, the observed 5-year survival rate was 15% and the median survival was 15 months. Serum-sodium ranged between 128 mmol/l and 146 mmol/l. Seventeen patients (14%) had sodium levels below normal range. In the multivariate analysis, serum-sodium was validated as an independent prognostic factor (HR 2.98, CI 1.54–5.77, p = 0.001). Conclusions: Low serum-sodium is a new, validated, independent prognostic factor in patients with metastatic RCC. No significant financial relationships to disclose.