Background: The clinical course of pT3 upper tract urothelial carcinoma (UTUC) is highly variable. Objectives: The aim of the current study was to validate the clinical and prognostic importance of pT3 subclassification in the renal pelvicalyceal system in a large international cohort of patients. Design, setting, and participants: From a multi-institutional international database, 858 renal pelvicalyceal tumors treated with radical nephroureterectomy (RNU) were systematically reevaluated by genitourinary pathologists. Category pT3 pelvic tumors were categorized as pT3a (infiltration of the renal parenchyma on a microscopic level only) versus pT3b (macroscopic infiltration of the renal parenchyma and/or infiltration of peripelvic adipose tissue). Intervention: RNU. Measurements: Associations of pT3 subclassifications with clinicopathologic features were assessed with the chi-square test. Prognostic impact was assessed with the log-rank test and multivariable Cox regression analyses. Results and limitations: Of 858 patients with renal pelvicalyceal tumors, 266 (31%) had pT3 disease. Of these, 146 (54.9%) were classified as pT3a and 120 (45.1%) as pT3b. Compared with pT3a, pT3b cancers were associated with higher tumor grade, nodal disease, and tumor necrosis. Ten-year recurrence-free (pT3a 58% vs pT3b 38%; p < 0.001) and cancer-specific (pT3a 60% vs pT3b 39%; p = 0.002) survival rates were lower for patients with pT3b disease. In multivariable analyses, classification pT3b was an independent predictor of both disease recurrence (hazard ratio [HR]: 1.8, p = 0.003) and cancer-specific mortality (HR: 1.7; p = 0.02). The major limitation is the retrospective character of the study. Conclusions: Subclassification of pT3 renal pelvicalyceal UTUC helps identify patients who are at increased risk of disease progression and cancer-related death. Further research may help assess the value of subclassification and its inclusion in future editions of the American Joint Committee on Cancer-International Union Against Cancer TNM classification system.
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