Accurately predicting the clinical prognosis of upper tract urothelial carcinoma (UTUC) seems crucial. We evaluated the effect of the involvement of urothelial bladder carcinoma (UBC) as a potential prognostic factor for overall survival (OS) and progression-free survival (PFS). The cohort included 115 patients with UTUC, subgrouped between January 2009 and December 2019 as follows: (1) only UTUC and (2) UTUC with synchronous or metachronous UBC (UTUC + UBC). Univariate and multivariate analyses were performed to identify independent prognostic factors for OS and PFS. Synchronous or metachronous UBC diagnosis in UTUC patients was an independent predictor of worse PFS (HR 3.326 CI 95% 1.474–7.503, p = 0.004), but it was not identified as a prognostic factor for OS (p > 0.05). Lymphovascular invasion (LVI) was associated with decreased PFS (HR 2.687 CI 95%1.172–6.163, p = 0.020) and OS (HR 4.980 CI 95%1.763–14.064, p = 0.002). This study indicates that concomitant or later UBC could predict a poor PFS, but it is not associated with a significantly worse OS in UTUC patients. The prognostic impact of LVI underlines its inclusion in the tumor staging system of UTUC.
