Genomic landscape of metastatic urothelial cancer in a multicenter Argentine cohort.

789 Background: Metastatic urothelial carcinoma (mUC) is a lethal disease with a heterogeneous genomic landscape. Most available genomic data derive from North America, Europe, or Asia, with Latin American (LATAM) patients largely underrepresented. Region-specific data are needed to inform precision oncology efforts and expand access to biomarker-driven trials. Methods: We conducted a retrospective, multicenter cohort study of patients with mUC who underwent genomic testing. Patients were included from eight academic and community centers across Argentina. Results: A total of 101 patients were included. Nearly half (45.5%; n = 46) presented with stage IV disease. Somatic mutation profiling was performed in all patients (100%) using multigene panel analysis. A potentially targetable mutation was identified in 63.4% (n = 64) of patients, while an ESCAT tier I alteration was detected in 33.7% (n = 34). FGFR2/3 alterations were observed in 24.7% (n = 25), HER2 amplification in 8.9% (n = 9), and PIK3CA mutations in 10.9% (n = 11). Only four patients with FGFR2/3 alterations received erdafitinib. With a median follow-up of 11.5 months (IQR, 14–19.1), the median progression-free survival (PFS) was 12.5 months (95% CI, 8.3–17.7), and the median overall survival (OS) was 24.2 months (95% CI, 16.3–NR). No statistically significant differences in PFS or OS were observed between patients with ESCAT alterations and those without (PFS: 8.3 vs 25.0 months, p = 0.08; OS: not reached vs 18.0 months, p = 0.39). Conclusions: This study provides one of the largest real-world genomic datasets of mUC in LATAM, underscoring the underrepresentation of patients from this region in genomic research. These findings highlight the need to improve access to biomarker-driven trials and precision oncology initiatives in Latin America.