The influence of body mass index on the long-term survival of patients with renal cell carcinoma after tumour nephrectomy

OBJECTIVE To assess whether under- or overweight at the time of surgery has any effect on the survival of the patients with renal cell carcinoma (RCC), as obesity increases the risk of developing RCC. PATIENTS AND METHODS We prospectively evaluated 780 patients who had nephrectomy for RCC between 1990 and 2005. We used uni- and multivariate Cox proportional hazards models to assess the effect of body mass index (BMI), tumour stage, Fuhrman grade, age, sex, histological type and performance status on cancer-specific survival (CSS). Patients were grouped according to BMI (in kg/m(2)), as underweight (< 18.5), normal (18.5-< 25), overweight (25-< 30) and obese (>= 30). RESULTS The median (range) follow-up was 5.3 (0.5-15.4) years, the patients being followed until June 2006; 254 patients died during the follow-up. Multivariate analyses of all patients showed that tumour stage, Fuhrman grade, Karnofsky performance status, age, sex and BMI were independent prognostic factors for CSS. While underweight patients had a significantly worse prognosis than those of normal weight, overweight or obese patients had a similar outcome to that of patients of normal weight. In a subgroup analyses including patients with localized RCC only, there was a strong tendency to less aggressive disease in the overweight group (P = 0.081). CONCLUSIONS Being underweight is an unfavourable and new risk factor for CSS in patients with RCC treated by nephrectomy. Although not significant, there seems to be a limited favourable prognostic effect of overweight on CSS in patients with localized RCC.