Tumor laterality in renal cancer as a predictor of survival in large patient cohorts: A STROBE compliant study.

To assess whether left and right-sided renal cell carcinoma (RCC) carry side-specific outcomes.Surgically treated RCC patients were included from the United States Surveillance, Epidemiology and End Results database (Surveillance, Epidemiology and End Results database [SEER]; 2013 version) and the German Centre for Cancer Registry Data (ZfKD; 2000-2014). Bilateral RCC, those with missing RCC staging, follow-up time, and survival status were excluded. Cancer-specific survival (CSS) according to RCC side was compared using multivariable Cox regression.Seventeen thousand seven hundred nine SEER patients and 41,967 ZfKD patients were included. In both datasets, patients with left-sided RCC had higher T status and more often presented with nodal positive or metastatic disease. In the SEER dataset 1258 (14.33%) patients with left-sided RCC underwent lymphadenectomy (LAD), compared to 908 (10.17%) LADs in right-sided RCC (P <.001). CSS was inferior for left-sided in both datasets after multivariable adjustment (SEER HR = 1.187, 95% CI 1.048-1.345, P = .007, P = .008; ZfKD HR = 1.155, 95% CI 1.046-1.275, P = .004).In the SEER population, site-specific CSS differences were driven by whether or not a LAD was performed. Among SEER patients with LAD no statistically significant differences in laterality were observed (HR 1.096, 95% CI 0.8977-1.337, P = .396) whereas, in absence of LAD, CSS was shorter for individuals with left-sided tumor (HR = 1.176, 95%CI 1.002-1.38, P = .0468).Although the overall survival difference was only marginal, left-sided RCC in surgically treated patients tends to present at more advanced stage and has in general worse CSS, especially in patients without LAD. Site-specific lymphogenic spread patterns might contribute to these findings. Further prospective studies should evaluate, whether side-adapted LAD protocols influence outcomes in RCC patients.