Growing evidence suggests that obesity, an established cause of renal cell cancer (RCC), may also be associated with a better prognosis. To evaluate the association between RCC survival and obesity, we analyzed a large cohort of patients with RCC and undertook a meta-analysis of the published evidence. We collected clinical and pathologic data from 1,543 patients who underwent nephrectomy for RCC between 1994 and 2008 with complete follow-up through 2008. Patients were grouped according to BMI (kg/m(2) ): underweight <18.5, normal weight 18.5 to <23, overweight 23 to <25 and obese ≥25. We estimated survival using the Kaplan-Meier method and Cox proportional hazard models to examine the impact of BMI on overall survival (OS) and cancer-specific survival (CSS) with adjustment for covariates. We performed a meta-analysis of BMI and OS, CSS and recurrence-free survival (RFS) from all relevant studies using a random-effects model. The 5-year CSS increased from 76.1% in the lowest to 92.7% in the highest BMI category. A multivariate analysis showed higher OS [hazard ratio (HR) = 0.45; 95% CI: 0.29-0.68) and CSS (HR = 0.47; 95% CI: 0.29-0.77] in obese patients than in normal weight patients. The meta-analysis further corroborated that high BMI significantly improved OS (HR = 0.57; 95% CI: 0.43-0.76), CSS (HR = 0.59; 95% CI: 0.48-0.74) and RFS (HR = 0.49; 95% CI: 0.30-0.81). Our study shows that preoperative BMI is an independent prognostic indicator for survival among patients with RCC.
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