Characterization of FGFR Alterations and Activation in Patients with High-Risk Non-Muscle-Invasive Bladder Cancer.

Purpose: The Genomic Analysis of High-Risk Non-Muscle-Invasive Bladder Cancer (GARNER) study investigated FGFR alteration (ALT) frequency and the clinical outcome relationship with Bacillus Calmette-Guérin (BCG) treatment in high-risk non-muscle-invasive bladder cancer (HR-NMIBC). An FGFR predictive response signature (FGFR-PRS) was discovered that identifies patients with an activated FGFR pathway who could potentially benefit from FGFR-targeted therapy beyond those who are FGFR ALT (+).

Experimental Design: Pretreatment tumor samples and clinical data were analyzed from 582 BCG-treated patients with HR-NMIBC. FGFR-PRS was discovered using a separate bladder cancer dataset and applied to the GARNER and other bladder cancer cohorts. FGFR-PRS was also applied to in vitro data from urothelial cancer cell lines treated with FGFR-active agents.

Results: A total of 31% of pretreatment GARNER HR-NMIBC tumors were FGFR ALT (+), but this was not significantly associated with BCG response. For the subset of patients with paired pre- and post-BCG treatment samples, nearly one-third of pretreatment ALT (+) patients were ALT (-) posttreatment. FGFR-PRS identified patients with an activated FGFR pathway and identified approximately twofold additional patients compared with ALT status alone, and this increase was similar across tumor stage. A positive relationship between tumor growth inhibition and FGFR-PRS score was shown in bladder cancer in vitro models treated with FGFR-active agents.

Conclusions: These data provide support for FGFR-targeted therapy use in FGFR ALT (+) HR-NMIBC and describe tumors with shared FGFR pathway-activated biology that is FGFR ALT (-) but FGFR-PRS (+). The latter suggests a broader potential patient population for FGFR-targeted therapy, which will require subsequent validation in patients treated with FGFR-targeted therapy.