Prognostic Implication of Body Mass Index on Survival Outcomes in Surgically Treated Nonmetastatic Renal Cell Carcinoma: A Single-Institutional Retrospective Analysis of a Large Cohort.

PURPOSE: Obesity is a well-known risk factor for renal cell carcinoma (RCC). However, the prognostic role of obesity in RCC has not been clearly established thus far. We aim to assess the effect of preoperative body mass index (BMI) on survival outcomes in nonmetastatic RCC patients. PATIENTS AND METHODS: We retrospectively analyzed data on 2329 patients who underwent curative surgery for RCC between 2000 and 2014 in a single institution. Patients were divided into normal (< 23 kg/m2), overweight (23-24.9 kg/m2), and obese (≥ 25 kg/m2) groups depending on cutoffs for Asian population. Kaplan-Meier analysis with log-rank test was used to estimate and compare survival outcomes, including recurrence-free, overall, and cancer-specific survival, among each BMI group. The influence of BMI on each survival outcome was evaluated using multivariate Cox regression analyses. RESULTS: Obese patients presented favorable 5-year recurrent-free (90.7% vs 84.9%, p < 0.001), overall (91.8% vs 86.8%, p = 0.002), and cancer-specific (94.8% vs 89.4%, p = 0.002) survival rates than the normal group. Multivariate analyses revealed that increasing BMI was an independent predictor of favorable survival outcomes (all p values < 0.05). In particular, overweight (p = 0.009) and obese (p = 0.009) patients showed better cancer-specific survival compared with normal patients. CONCLUSIONS: Our data suggest that overweight and obesity defined based on BMI are generally related to favorable survival outcomes after surgery for RCC. Additional basic research is required to find out the biological mechanisms explaining the correlation between BMI and survival outcomes.