Impact of body mass index on clinicopathological outcomes in patients with renal cell carcinoma without anorexia-cachexia syndrome

Although obesity defined by a high body mass index (BMI) is generally associated with increased risk of renal cell carcinoma (RCC), low BMI has paradoxically been associated with increased tumor aggressiveness and poor prognosis. As anorexia-cachexia syndrome (ACS) is associated with decreased BMI and is frequently observed in patients with advanced RCC, the present study investigated the association of BMI with tumor aggressiveness and prognosis in RCC in relation to ACS. The association of BMI with clinicopathological parameters was analyzed in 503 consecutive patients who underwent surgery for RCC. Kaplan-Meier curves and rates of overall survival (OS) stratified by BMI were also compared in relation to the presence or absence of ACS, defined as the presence of anorexia or malaise, and/or weight loss and/or hypoalbuminemia. Low BMI was significantly associated with high-grade tumors (P=0.0027) and the presence of distant metastasis (P=0.0025), and patients with a lower BMI had significantly shorter OS than those with a higher BMI (P=0.0441). Patients with ACS had a significantly lower BMI (mean, 21.5 kg/m2) than those without ACS (mean, 23.5 kg/m2; P<0.0001) and had significantly shorter OS than those without ACS (P<0.0001). On multivariate analysis, ACS was an independent predictor of short OS [P=0.0089; hazard ratio (HR), 2.21; 95% confidence interval (CI), 1.22-3.92] and short cancer-specific survival (P=0.0308; HR, 2.03; 95% CI, 1.07-3.78); however, BMI was not (P=0.5440 and P=0.6804, respectively). In the 413 patients without ACS at initial presentation, BMI was not associated with any clinicopathological parameters or OS (log-rank, P=0.4591). BMI itself was not a predictor of survival in patients without ACS, and the association between low BMI and increased tumor aggressiveness and poor prognosis could be due to ACS.