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

Purpose: 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. Patients and methods: We retrospectively analyzed 643 consecutive patients with non-metastatic 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. Results: Males were more likely to have a higher BMI than females (BMI as a categorical variable: P< 0.001; BMI as a continuous variable: P=0.002). In men, a high BMI was significantly correlated with better 5-year OS, CSS, and MFS rates (P=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, P=0.011; CSS: HR=0.225, P=0.005; MFS: HR=0.243, P=0.004). However, in women, there was no significant difference in 5-year OS, CSS, and MFS rates according to BMI (P=0.781, 0.812, and 0.538, respectively). Moreover, a high BMI was no longer independently associated with OS, CSS, or MFS (P=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 P< 0.05) and not among women (all P> 0.05). Conclusion: 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.