LAUSR

473 Background: Several IO agents have been approved for treatment of advanced urothelial cancer pts. We investigated the association between sites of mets and CO in urothelial cancer pts treated with IO in the real world setting. Methods: We performed a retrospective review of 67 urothelial cancer pts treated with PD-1 or PD-L1 inhibitors at Winship Cancer Institute from 2015-2018. Overall survival (OS) and progression free survival (PFS) were measured from first dose of IO to date of death or hospice referral and radiographic or clinical progression, respectively. Sites of mets were collected from radiology and clinic notes at baseline. Univariate analysis (UVA) and multivariable analysis (MVA) used Cox proportional hazard. Results: The median age was 70 and most (79.1%) were men. Pts had mets to sites such as lymph node (73.1%), bone (29.9%), liver (20.9%), lung (31.3%), and brain (1.5%). Pts with bone or liver mets had significantly shorter OS and PFS in UVA. Pts with bone mets also had significantly shorter OS and PFS in MVA (Table). The median OS of pts with bone mets was 2.2 months (12-month survival=28.0%), while those without bone mets had a median OS of 21.9 months (12-month survival=52.5%) per Kaplan-Meier estimation. The median OS of pts with liver mets was 2.2 months (12-month survival=28.6%), while those without liver mets had a median OS of 12.8 months (12-month survival=50.1%) per Kaplan-Meier estimation. Conclusions: Bone and liver mets are poor prognostic factors in urothelial cancer pts receiving IO in the real world setting. These findings should be validated in a larger study. [Table: see text]