Purpose: Leptin, an adipocyte derived cytokine that is closely associated with obesity, was recently shown to be involved in carcinogenesis and cancer progression. Because obesity is a significant risk factor for renal cell carcinoma, we investigated the link between leptin and the development of renal cell carcinoma. Materials and Methods: Associations between preoperative serum leptin levels and leptin receptor expression in tumor specimens and various clinicopathological parameters were analyzed in 57 patients with renal cell carcinoma. Results: Serum leptin levels were 1.2 to 16.2 ng/ml (mean 4.5). Of 57 tumors 22 (38.6%) demonstrated high leptin receptor expression. Serum leptin levels were significantly higher in patients with vs without tumor specimen venous invasion (p = 0.030) and higher in patients with high vs low leptin receptor expression (p = 0.019). There were significant associations between high leptin receptor expression and the presence of venous invasion (p = 0.013), histological type (p = 0.0076) and regional lymph node metastasis (p = 0.047). Of 42 patients with N0M0 disease those with serum leptin 5.0 ng/ml or more had significantly shorter progression-free survival than patients with lower levels (p = 0.0043). Multivariate Cox proportional hazards model analysis demonstrated that higher serum leptin was an independent predictor of progression-free survival (p = 0.0406). Conclusions: Leptin and leptin receptor could have a key role in the invasion of renal cell carcinoma and they could be valuable predictors of progression.
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