陳人傑¹、黃逸修^1,2、黃子豪^1,2、魏子鈞^1,2、黃奕燊^1,2、范玉華^1,2、林志杰^1,2、林子平^1,2、
鍾孝仁^1,2、盧星華^1,2、郭俊逸^1,2、吳宏豪^1,2、黃志賢^1,2、張延驊^1,2、林登龍^1,2

臺北榮民總醫院 泌尿部¹; 國立陽明大學醫學院 泌尿學科 書田泌尿科學研究中心²

Jen-Chieh Chen¹, Eric Y.H. Huang^1,2, Tzu-Hao Huang^1,2, Tzu-Chun Wei^1,2, I-shen Huang^1,2,
Yu-Hua Fan^1,2, Chi-Chieh Lin^1,2, Tzu-Ping Lin^1,2, Hsiao-Jen Chung^1,2, Shing-Hwa Lu^1,2,
Junne-Yih Kuo^1,2, William J. Huang^1,2, Howard H.H. Wu^1,2, Yen-Hwa Chang^1,2, Alex T.L. Lin^1,2

Department of Urology, Taipei Veterans General Hospital¹;

Department of Urology, School of Medicine and Shu-Tien Urological Science Research Center, National Yang-Ming University, Taipei, Taiwan²

 

Controversies exist in the prognosis regarding the impact of body mass index (BMI) of the patients with upper urinary tract urothelial carcinoma (UTUC) underwent radial nephroureterectomy (RNU). Western studies showed that higher BMI was a poor prognostic factor but Asian data suggested that obesity paradox might have existed in Asian patients. A growing literature revealed the obesity paradox observed in some solitary malignancy was age-dependent. Herein, we assessed the age-dependent prognostic value of BMI in patient with UTUC treated with RNU by analyzing our single institute database.

From January 2010 to December 2017, a total of 468 patients with UTUC underwent RNU with curative intent were enrolled. BMI was measured prior to surgery and was categorized as underweight (BMI < 18.5 kg/m²), normal (18.5 kg/m² ≤ BMI < 25 kg/m²), overweight (25 kg/m² ≤ BMI < 30 kg/m²), and obese (BMI ≥ 30 kg/m²) according to the World Health Organization's recommendations. We divided the patients into 2 groups as the younger and older group for further analysis. The age cut-off was determined as 70 years based on previous study. The overall survival, cancer-specific survival, and disease-free survival were investigated. Pearson’s chi-square test, Kaplan-Meier method, and Cox proportional hazards regression model were used to analyze the data.

The median follow-up was 36 months. The mean BMI was 24.5 kg/m² with 24 patients underweight, 251 normal, 157 overweight, and 40 obese. There were 197 patients in the younger group (age < 70) and 271 patients in the older group (age ≥ 70). The older group patients were significantly more likely to have lymphovascular invasion (younger group: 4.1%; older group: 9.2%, p = 0.03). Other clinicopathological features were not different between groups, including gender, BMI, smoking, pathologic T stage, lymph node positivity, tumor grade, multifocality, presence of poor histological feature, presence of concomitant carcinoma in situ (CIS), and type of surgery. The median follow up period was significantly longer in younger group (younger group: 41 months; older group: 33 months, p = 0.02). For the whole patient cohort, multivariate cox regression analysis revealed that older age (≥ 70 years) was an independent predictor for poor overall survival (Hazard ratio = 1.74, p = 0.001) and there were no survival difference between those who had higher BMI (≥ 25 kg/m²) and lower BMI (< 25 kg/m²). This finding indicated that the impact of age on survival was stronger than BMI, which was compatible with previous study. However, if we divided the patient into younger group and older group, we found that the patients in younger group with higher BMI (≥ 25 kg/m²) had better disease-free survival (DFS) (p = 0.022). In older group, no BMI related survival differences were observed. Multivariate Cox regression analysis in the younger group showed that higher pre-operative BMI (≥ 25 kg/m²) was an independent predictor for DFS (Hazard ratio = 0.53, p = 0.050). Other independent predictors for DFS in the younger group included tumor location, tumor stage, lymph node positivity, presence of poor histological feature, and presence of lymphovascular invasion.

We found an age-dependent prognostic value of BMI in patient with UTUC treated with RNU. Younger patients (< 70 years) with higher BMI (≥ 25 kg/m²) was associated with a favorable DFS. However, no BMI related survival differences were found in older patients. Pre-operative BMI may provide additional prognostic information to establish risk factors especially in younger patients.