Pathological subclassification of T3 upper tract urothelial carcinoma: Complementary evidence for existing guidelines.

841 Background: According to the current guidelines, upper tract urothelial carcinoma (UTUC), which encroaches beyond the muscularis propria but does not invade peripheral organs or perirenal fat, is classified as pathological T3 (pT3). However, the current classification definition of pT3 fails to meet clinical needs due to the significant heterogeneity of pT3 UTUC in terms of biological features and oncological outcomes. Therefore, the aim of this study was to explore the effect of subclassifying pT3 UTUC on oncological outcomes based on a large UTUC cohort from Southwest China. Methods: Data of pathologically confirmed UTUC patients treated with radical nephroureterectomy (RNU) treatment at West China Hospital of Sichuan University from May 2003 to June 2019 were retrospectively collected. Only patients with a diagnosis of initial pT3 and complete follow-up information were included in the study. pT3 was subclassified into pT3a (defined as tumor invasion of the ureteral adventitia or renal parenchyma) and pT3b (defined as tumor invasion of the ureter or peri-pelvic fat). The primary endpoints included cancer-specific survival (CSS), overall survival (OS) and recurrence-free survival (RFS). Results: A total of 326 patients with initial pT3 UTUC were finally included. According to our proposed subclassification, 232 cases were in pT3a group and 94 cases were in pT3b group. K-M analysis showed that the patients in pT3b group had significantly worse OS, CSS and RFS than those in pT3a group. Multifactorial Cox regression analysis demonstrated that patients in pT3b group had a 1.86-fold (95% CI, 1.19-2.91) risk of death, a 1.95-fold (95% CI, 1.21-3.17) risk of disease-related death and a 1.78-fold (95% CI, 1.21-3.17) risk of disease recurrence than those in the pT3a group. After adjustment for tumor size, tumor grade and lymph node metastasis the above findings remained statistically significant. Conclusions: Based on the presence or absence of invasion of the ureter and peri-pelvic fat, our study proposes a novel pT3 subclassification, which provide physicians with invaluable insight into better stratification of pT3 UTUC patients and provide a basis for individualized treatment.