Concomitant carcinoma in situ as a prognostic factor in the upper tract urothelial carcinoma after radical nephroureterectomy: A systematic review and meta-analysis.

•Concomitant carcinoma in situ (CIS) is associated with worse survival outcomes in upper tract urothelial carcinoma (UTUC).•Concomitant CIS is an independent prognostic risk factor in UTUC.•Recurrence rate of UTUC is 30.5% and the mortality rate is 20.9%.•Concomitant CIS accounts for 12.79% of UTUC.