The influence of sex on the prognostic value of body mass index in non-metastasis renal cell carcinoma.

The prognostic value of obesity in patients with renal cell carcinoma (RCC) remains controversial. This study aimed to assess the sex-dependent prognostic role of body mass index (BMI) in patients with nonmetastatic RCC who underwent radical or partial nephrectomy. We retrospectively analyzed 643 consecutive patients with nonmetastatic RCC who underwent curative nephrectomy in our center between 2004 and 2014. Associations among BMI, sex, overall survival (OS), cancer-specific survival (CSS), and metastasis-free survival (MFS) were analyzed. Males were more likely to have a higher BMI than females (BMI as a categorical variable: <0.001; BMI as a continuous variable: =0.002). In men, a high BMI was significantly correlated with better 5-year OS, CSS, and MFS rates (=0.001, 0.014, and 0.001, respectively), and multivariate analysis identified that a high BMI was independently associated with greater OS, CSS, and MFS (OS: hazard ratio [HR]=0.207, =0.011; CSS: HR=0.225, =0.005; MFS: HR=0.243, =0.004). However, in women, there was no significant difference in 5-year OS, CSS, and MFS rates according to BMI (=0.781, 0.812, and 0.538, respectively). Moreover, a high BMI was no longer independently associated with OS, CSS, or MFS (=0.821, 0.832, and 0.801, respectively). Among patients with clear cell RCC, BMI was significantly associated with OS, CSS, and MFS only among men (all <0.05) and not among women (all >0.05). Among patients with nonmetastatic RCC, a high BMI was a favorable prognostic factor in males rather than females. Therefore, sex might influence the correlation between obesity and urological outcomes in nonmetastatic RCC.