Hyponatremia as a powerful prognostic predictor for Japanese patients with clear cell renal cell carcinoma treated with a tyrosine kinase inhibitor

Background We aimed to evaluate the prognostic significance of hyponatremia in patients with metastatic clear cell renal cell carcinoma (RCC) treated with a tyrosine kinase inhibitor (TKI). Methods This study included a total of 209 consecutive Japanese patients undergoing radical nephrectomy who were subsequently treated with either sunitinib or sorafenib as a first-line therapy for metastatic clear cell RCC. In this series, normal natremia and hyponatremia prior to the introduction of TKI was defined as a serum sodium level >136 and ≤136 mEq/L, respectively. Results Patients were classified into 165 (78.9 %) with normal natremia and 44 (21.1 %) with hyponatremia. Progression-free survival (PFS) in the hyponatremia group (median 10.0 months) was significantly poorer than that in the normal natremia group (median 28.4 months). Overall survival (OS) in the hyponatremia group (median 20.9 months) was significantly poorer than that in the normal natremia group (median 38.5 months). Multivariate analyses identified hyponatremia, in addition to the existence of sarcomatoid components in radical nephrectomy specimens, high serum C-reactive protein levels, and low serum albumin levels, as poor prognostic factors for both PFS and OS. There were significant differences in both PFS and OS according to the number of these 4 independent risk factors that were positive (negative for any risk factors vs positive for 1 or 2 risk factors vs positive for 3 or 4 risk factors). Conclusions Hyponatremia appears to be one of the most powerful prognostic predictors in Japanese patients treated with a TKI as a first-line agent against metastatic clear cell RCC.