Comprehensive genomic sequencing of urothelial tumors to identify rare driver genomic alterations in SMARCB1 in a subset of patients.

385Background: Multiple genomic alterations leading to overlapping dysregulation of cell cycle, kinase and phosphotidyl \inositol-3-OHkinase signaling and chromatin remodeling are the hallmark of urothelial carcinoma (UC). ARID1A and SMARCA2 loss are frequently altered leading to SWI/SNF nucleosome-remodeling complex dysregulation in urothelial cancers. Mutations affecting components of the SWI/SNF complex lead to aggressive de-differentiated neoplasms. SMARCB1 loss has been implicated in malignant rhabdoid tumors, epithelioid sarcoma and renal medullary carcinoma. Upper tract UC patients with SMARCB1 loss may represent a novel, rare subset. Methods: Tissue from UC patients (n=1099) was assayed by hybrid-capture based comprehensive genomic profiling (CGP) in the course of clinical care to evaluate genomic alterations (GA: base substitutions, indels, amplifications, copy number alterations, fusions/rearrangements) and targeted therapy opportunities; 315 genes frequently altered in cancer were assayed. One ...