To identify whether the body mass index (BMI) has any adverse effect on the prognosis of patients with established renal cell carcinoma, given the increasing prevalence of obesity and the rising incidence of renal cell carcinoma in the United States.

We reviewed the records of patients who underwent nephrectomy for localized disease between 1985 and 1998 at our institution. Patients were grouped according to BMI as normal (less than 25 kg/m²), overweight (25 to 30 kg/m²), or obese (more than 30 kg/m²). Cox regression analysis was used to determine the significant predictors of metastasis and survival.

A total of 400 patients met the inclusion criteria. On univariate analysis, normal BMI (P = 0.018), pathologic stage (P <0.0001), Fuhrman grade (P = 0.007), maximal tumor size (P = 0.005), and time to recurrence (P <0.0001) were significant predictors of disease-specific death. On multivariate regression analysis, the time to metastasis (P <0.0001) was the best predictor of disease-specific death, followed by BMI (normal versus overweight or obese; P = 0.006) and pathologic stage (P = 0.007). Patients with a normal BMI who had pathologic Stage pT3 or greater and developed metastasis within 19 months of surgery had the worst prognosis, with a disease-specific death rate of 52.0%.

Our findings suggest that overweight and obese patients with renal cell carcinoma have a more favorable prognosis than patients with a normal BMI. If others confirm our finding that a high BMI confers a survival advantage to patients undergoing nephrectomy, BMI may prove to be an important prognostic factor in renal cell carcinoma.