LAUSR

449Background: Despite similarities between upper-tract (UTUC) and bladder urothelial carcinoma (BUC), distinctive clinicopathologic and genomic differences are being described. We further investigate the genomic landscape of these two interrelated malignancies in same-patient metachronous (m) UTUC and BUC using next generation sequencing (NGS). Methods: Following institutional board approval, UTUC and BUC samples were obtained from patients via surgical resection or endoscopic biopsy. Tumors were macrodissected from unstained formalin-fixed, paraffin-embedded slides. Study inclusion was untreated patient samples of UTUC and/or BUC divided into 4 groups: 1) UTUC with mBUC, 2) BUC with mUTUC, 3) Synchronous BUC and UTUC, 4) UTUC with no bladder history. Exclusions were for inadequate clinical data or histological tumor purity < 30%. Whole transcriptome RNA sequencing was performed and analyzed using BASE47 panel (includes basal, luminal, p53-like and cell cycle genes). Results: A total of 95 (UTUC = 61, BU...