Effect of a variant histology on the oncological outcomes of Japanese patients with upper tract urothelial carcinomas after radical nephroureterectomy: a multicenter retrospective study

Background: An earlier systematic review and meta-analysis found that patients with a certain histological variant of upper tract urothelial carcinoma (UTUC) exhibited more advanced disease and poorer survival than those with pure UTUC. A difference in the clinicopathological UTUC characteristics of Caucasian and Japanese patients has been reported, but few studies have investigated the clinical impact of the variant histology in Japanese UTUC patients. Methods: We retrospectively enrolled 824 Japanese patients with pTa-4N0-1M0 UTUCs who underwent radical nephroureterectomy without neoadjuvant chemotherapy. Subsequently, we explored the effects of the variant histology on disease aggressiveness and the oncological outcomes. We used Cox's proportional hazards models to identify significant predictors of oncological outcomes, specifically intravesical recurrencefree survival (IVRFS), recurrence-free survival (RFS), cancer-specific survival (CSS), and overall survival (OS). Results: Of the 824 UTUC patients, 32 (3.9%) exhibited a variant histology that correlated significantly with a higher pathological T stage and lymphovascular invasion (LVI). Univariate analysis revealed that the variant histology was an independent risk factor for suboptimal RFS, CSS, and OS. However, significance was lost on multivariate analyses. Conclusions: The variant histology does not add to the prognostic information imparted by the pathological findings after radical nephroureterectomy, particularly in Japanese UTUC patients.