458 Background: Fibroblast growth factor receptor (FGFR) inhibitors are a promising new targeted therapy for patients with metastatic urothelial cancer (UC) and FGFR alterations. FGFR-altered tumors are more likely to be of the luminal molecular subtype, which is less immune infiltrated and may be less likely to respond to immune checkpoint inhibitors (ICP). Methods: Metastatic UC patients at the University of North Carolina who underwent targeted exon sequencing (any CLIA-certified platform) and were treated with ICP since 2014 were identified. Patients with any FGFR alteration were compared to patients without alterations (including mutations, fusions, and amplifications in FGFR1-4). Overall response rates (ORR) to ICP were assessed by a radiologist (K.M.) per RECIST 1.1 and compared between FGFR-altered and unaltered tumors using Fisher’s exact tests. Patients who died prior to radiologic assessment were considered non-responders. Results: 66 patients (median age 70, 65% male, 76% white, 21% black) were identified. Most patients (74%) had received prior platinum-based chemotherapy, and 13% had received 2 or more prior lines of therapy. At the time of initiation of ICP, 32% of patients had a hemoglobin < 10, 33% had liver metastases, and 72% had a performance status > 0. Fifteen (22%) patients had FGFR alterations. The ORR for all patients was 15%, with ORR of 13% in FGFR-altered patients compared with 16% in unaltered patients (p = 1.0). No patients (0/9, 0%) with known pathogenic mutations in FGFR3 responded to ICP compared to 10/57 (18%) of patients without these alterations (p = 0.33). 46% of FGFR-altered patients who stopped ICP due to progression received subsequent therapy. Conclusions: Response rates to ICP are low and there was no difference in ORR between FGFR-altered and unaltered patients. While no patient with pathogenic FGFR3 mutations responded to ICP in our cohort, this difference did not reach statistical significance. Given low response rates overall, some FGFR-altered patients may benefit from treatment with FGFR inhibitors prior to ICP. Analysis of larger cohorts of patients as well as patients from clinical trials and more in-depth molecular profiling may add further clarity.
Fibroblast growth factor receptor 3 activation plays a causative role in urothelial cancer pathogenesis in cooperation withPtenloss in mice
