Characterization of actionable genetic alterations to guide targeted therapy for metastatic urothelial carcinoma.

Abstract

407 Background: Genetic alterations predicting response to targeted therapy are an area of active interest in developing novel therapies for patients with metastatic urothelial carcinoma (mUC). With the objective of characterizing the frequency of actionable alterations (AA) and the evidence supporting targeted therapy for these AAs, we report our experience with next-generation sequencing in mUC. Methods: Patients with sequenced mUC lesions were identified from our prospectively-maintained database. All AAs with clinical or biologic evidence supporting the alteration as predicting response to targeted therapy were identified and stratified by Oncology Knowledge Base (OncoKB) level of evidence (table). The relationship between strength of evidence and administration of targeted therapy was examined. Results: Ninety-nine of 134 patients (74%) harbored at least one AA, with 162 total AAs identified. Twenty level 2B AAs were identified, reflecting the highest level evidence in this cohort, with ERBB2 amplification (9), TSC1/TSC2 (6), and BRCA1/BRCA2 mutations (3) most common. Twenty-eight level 3A, 51 level 3B, and 62 level 4 AAs were also identified. Seventeen patients received targeted therapy, which was administered with greater frequency among patients with level 3B or higher AAs (21% vs 3%). Conclusions: Most patients with mUC harbor at least one AA, suggesting multiple targeted therapeutic opportunities in mUC. These findings highlight the need for additional clinical trials and the role of genetic testing in identifying candidates for targeted therapy. [Table: see text]