What's known on the subject? and What does the study add? Tumour stage is a powerful predictor of clinical outcomes and the most important factor driving clinical decision-making after radical nephroureterectomy (RNU) in upper tract urothelial carcinoma (UTUC). It has been suggested that renal pelvic pT3 subclassification into microscopic infiltration of the renal parenchyma (pT3a) versus macroscopic infiltration or invasion of peripelvic adipose tissue (pT3b) has strong prognostic value. This is an external validation study of the prognostic value of pT3 subclassification of renal pelvic UTUC in a large international cohort of patients treated with RNU. pT3b UTUC is associated with features of aggressive tumour biology, disease recurrence and cancer-specific mortality. However, pT3 subclassification is not an independent predictor of clinical outcomes.
