Differential effect of body mass index by gender on oncological outcomes in patients with renal cell carcinoma

Objectives: To investigate the relationship between gender, body mass index (BMI), and prognosis in renal cell carcinoma (RCC) patients. Materials and Methods: We retrospectively reviewed 1353 patients with RCC who underwent a partial or radical nephrectomy between 1988 and 2015. The association among sex, BMI, stage, grade, overall survival (OS), and recurrence-free survival (RFS) was analyzed. Results: The median age of the patients was 59.4 +/- 11.9 years. Female patients had proportionally lower grade tumors than male patients (Grade I-II in 75.5% vs. 69.3% in women and men, respectively, P = 0.022). There was no relationship between Fuhrman grade and BMI when substratified by gender (P > 0.05). There was a nonsignificant trend toward more localized disease in female patients (P = 0.058). There was no relationship between T stage and BMI when stratified by gender (P > 0.05). Patients with higher BMI had significantly better OS (P = 0.0004 and P = 0.0003) and RFS (P = 0.0209 and P = 0.0082) whether broken out by lower 33rd or 25th percentile. Male patients with higher BMI had significantly better OS and RFS rates. However, there was no relationship between BMI and OS or RFS for female patients (P > 0.05). Multivariate analysis of the entire cohort demonstrated that a BMI in the lower quartile independently predicts OS (hazard ratio 1.604 [95% confidence interval: 1.07-2.408], P = 0.022) but not RFS (P > 0.05). When stratified by gender, there was no relationship between BMI and either OS or RFS (P > 0.05). Conclusions: Increasing BMI was associated with RCC prognosis. However, the clinical association between BMI and oncologic outcomes may be different between men and women.