Survival Impact of Variant Histology Diagnosis in Upper Tract Urothelial Carcinoma.

PURPOSE: Little is known regarding the prognostic implications of variant histology in upper tract urothelial carcinoma (UTUC). We sought to evaluate the impact of variant histology UTUC on patient survival outcomes at our institution. MATERIALS AND METHODS: We identified 705 patients who underwent nephroureterectomy for UTUC at our institution between January 1995 and December 2018. We tested the association between variant histology and cancer-specific survival (CSS) and overall survival (OS) using separate multivariable Cox models after adjusting for pathological stage. RESULTS: Forty-seven patients (6.7%) had variant histology, with prevalence increasing over time (p=0.003). Other demographic and surgical characteristics were similar between variant histology and pure urothelial carcinoma groups. While patients with variant histology were more likely to receive neoadjuvant chemotherapy (38% vs 15%, p <0.001), they were also more likely to have a higher pathological T stage (p <0.001). Variant histology was associated with significantly worse CSS (HR: 2.14; 95% CI 1.33, 3.44; p=0.002) and OS (HR: 1.74; 95% CI 1.15, 2.63; p=0.008). After adjusting for pathological T stage, variant histology was not significantly associated with CSS (HR: 1.17; 95% CI 0.72, 1.89; p=0.5) or OS (HR: 1.20; 95% CI 0.79, 1.84; p=0.4). CONCLUSIONS: Variant histology UTUC is associated with advanced stage and poor survival, and could serve as a useful biomarker for high-risk disease when pathological stage is unknown. However, the inferior CSS and OS with variant histology can be explained by the higher tumor stage on nephroureterectomy. Thus, finding variant histology on surgical pathology does not provide additional prognostic information beyond stage.