There is currently only one published prospective study testing the benefit of adjuvant chemotherapy in upper tract urothelial carcinoma (UTUC), named the Peri-Operative chemotherapy versus sUrveillance in upper Tract urothelial cancer (POUT III) study [1]. The primary objective of this trial was to examine whether adjuvant chemotherapy improves disease-free survival for patients with resected histologically confirmed muscle invasive (pT2-T4, N0-3) or node positive UTUC [2]. Based off this level-one evidence, the latest 2022 European Association of Urology (EAU) guidelines now strongly recommend the usage of post-operative systemic platinum-based chemotherapy in patients with high-risk non-metastatic UTUC [3]. Similarly, the NCCN guidelines recommend that adjuvant therapy should be discussed with patients harboring pT3-4 or nodal disease, specifically a platinum-based regimen, based on this data [4]. Notably, the generalizability of the POUT III trial has not been externally validated in a population-based cohort. For any RCT to be externally valid, its supposedly randomly selected sample must be representative of the general population seen in everyday clinical practice. Thus, the aim of our present study was to assess this European randomized controlled trial's generalizability (external validity) to a large, North American cohort, using a nationwide database.