Can body mass index predict survival outcomes in patients treated with radical nephroureterectomy for upper-tract urothelial carcinoma?

Purpose: To assess the relationship between body mass index (BMI) and survival outcomes in Korean patients with upper-tract urothelial carcinoma (UTUC). Methods: A single-institutional retrospective analysis was conducted using clinical and pathological data of 445 UTUC patients who had undergone radical nephroureterectomy with bladder cuff excision from 1997 to 2012. Enrolled patients were classified into normal weight (BMI < 23 kg/m²), overweight (BMI 23–24.9 kg/m²), and obese (BMI ≥ 25 kg/m²) in accordance with BMI cutoffs for Asian populations. The impact of BMI on intravesical recurrence (IVR)-free survival, overall survival (OS), and cancer-specific survival (CSS) was evaluated using Kaplan–Meier analysis with the log-rank test and the Cox proportional hazard model. Results: The median BMI of all patients was 24.2 kg/m² (interquartile range 22.2–25.8). There were no significant differences in the IVR-free survival rates according to BMI classification (p = 0.488). The 5-year OS and CSS rates were 58.8, 66.3, and 76.3 % (p = 0.057) and 67.4, 69.3, and 81.5 % (p = 0.021) in the normal, overweight, and obese groups, respectively. In the univariate analysis, obesity (BMI ≥ 25 kg/m²) was a significant predictor of better OS [hazard ratio (HR) 0.63; 95 % confidence interval (CI) 0.43–0.92, p = 0.017] and CSS (HR 0.53; 95 % CI 0.33–0.84, p = 0.007) than normal weight. However, these associations could not be confirmed in the multivariable analysis after adjusting for other clinicopathological factors, such as tumor stage, tumor grade, lymphovascular invasion, and surgical margin. Conclusions: Our study results are inconclusive, in that, the multivariate analysis did not identify the influence of BMI on survival, although higher BMI appears clinically associated with favorable survival outcomes in Korean patients with UTUC.