Molecular markers to predict response to selective fibroblast growth factor receptor inhibitors (FGFRinh) in patients (pts) with FGFR-amplified (amp) or mutated (mut) tumors.

2581Background: Several FGFR and ligand (11q) alterations have been described in cancer. While FGFR fusions are recognized biomarkers of response to FGFRinh, it is still unclear to what extent FGFRamp, FGFR mRNA high expression (mRNAh) or FGFRmut predict sensitivity in the clinic. Methods: Retrospective analysis of pts with molecularly-selected FGFRamp/mRNAh/mut tumors treated with FGFRinh in phase 1 trials at our institution. Mut were detected with IlluminaO or Foundation OneO. FGFR1-2amp were analyzed by in situ hybridization and mRNA levels by qRT-PCR or nCounterO. Clinical benefit (ClinBen) was defined as any tumor shrinkage plus disease control for ³ 4 months (m). Time to progression (TTP) was defined as time between start of FGFRinh and end for any cause. Results: From 2011 to 2016, 36 pts with FGFRamp(25)/mRNAh(5)/mut(6) received an FGFRinh (irreversible- [11 cases (c)] or reversible-FGFR1-4inh [23 c], isoform-specific FGFRinh [3 c] or combo with PI3Kinh [1 c]). Median age 55 yrs (34-76); median pr...