Interethnic differences in the impact of body mass index on upper tract urothelial carcinoma following radical nephroureterectomy.

PURPOSE: Inconsistent prognostic implications of body mass index (BMI) in upper tract urothelial carcinoma (UTUC) have been reported across different ethnicities. In this study, we aimed to analyze the oncologic role of BMI in Asian and Caucasian patients with UTUC. METHODS: We retrospectively collected data from 648 Asian Taiwanese and 213 Caucasian American patients who underwent radical nephroureterectomy for UTUC. We compared clinicopathologic features among groups categorized by different BMI. Kaplan-Meier method and Cox regression model were used to examine the impact of BMI on recurrence and survival by ethnicity. RESULTS: According to ethnicity-specific criteria, overweight and obesity were found in 151 (23.2%) and 215 (33.2%) Asians, and 79 (37.1%) and 78 (36.6%) Caucasians, respectively. No significant association between BMI and disease characteristics was detected in both ethnicities. On multivariate analysis, overweight and obese Asians had significantly lower recurrence than those with normal weight (HR 0.631, 95% CI 0.413-0.966; HR 0.695, 95% CI 0.493-0.981, respectively), and obesity was an independent prognostic factor for favorable cancer-specific and overall survival (HR 0.521, 95% CI 0.342-0.794; HR 0.545, 95% CI 0.386-0.769, respectively). There was no significant difference in outcomes among normal, overweight and obese Caucasians, but obese patients had a relatively poorer 5-year RFS, CSS, and OS rates of 52.8%, 60.5%, and 47.2%, compared to 54.9%, 69.1%, and 54.9% for normal weight patients. CONCLUSION: Higher BMI was associated with improved outcomes in Asian patients with UTUC. Interethnic differences could influence preoperative counseling or prediction modeling in patients with UTUC.