FGFR2: A pan-genomic target.

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3099 Background: FGFR2 genomic alterations (GA) have been described in a variety of solid tumors and emerged as biomarkers for investigational agents undergoing clinical trials. Methods: 201,766 primarily relapsed/refractory malignancies were evaluated with a hybrid-capture based sequencing assay Tumor mutational burden (TMB) was determined on 0.8-1.1 Mbp of sequenced DNA and reported as mut/Mb. Microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3 antibody). Results: FGFR2 GA were detected in 2,993 (1.5%) cases featuring short variant (SV) mut (42%), copy number changes (27%), rearrangements/fusions (28%) and multiple GA (3%). The most frequent SV GA were S252W, N549K, C382R, P253R, Y375C, K659E and R664W. A small cohort (2%) of tumors featured the V564I and V564L GA that are associated with resistance to TKI drugs. The FGFR2-altered cases were 69% female/31% male with median age of 61 yrs. Most frequent GA in FGFR2 altered cancers: TP53 (47%), PIK3CA (22%), PTEN (20%), ARID1A (18%), CDKN2A/2B (18/14%) and MYC (12%). FGFR2 SVs most common in endometrial, breast carcinomas (ca) and CUP. FGFR2 amplification most common in breast, gastroesophageal and lung ca. FGFR rearrangement/fusions most common in cholangioca (37%), CUP (15%), pancreatobiliary (12%) and breast ca (6%). The FGFR2- BICC1 was the most frequent fusion followed by fusions with TACC2, AHCYL1, CCDC6, VCL, and KIAA1217. MSI-High status present in 6.8% of evaluable FGFR2 altered cases (63% in endometrial ca). Median TMB was 3.5 mut/Mb with 21.8% featuring ≥ 10 mut/Mb and 12.0% featuring ≥ 20 mut/Mb. Only 63% of MSI-High FGFR2 mut tumors had TMB ≥ 20 mut/Mb. 12.7% FGFR2 mut+ had > 1% PD-L1 staining with 3.4% > 50% staining. 29% of PD-L1 IHC+ cases in NSCLC. FGFR mut ca’s responding to anti-FGFR2 therapies will be presented. Conclusions: FGFR2 GA are most frequent in cholangioca, breast, GI tract, lung ca and CUP, with enrichment of FGFR2 fusions in biliary tract ca. Cases with FGFR2 GA typically do not feature other kinase driver GA and are associated with mut in the MTOR/PIK3CA/AKT pathways. Finally, in contrast with RTK driver GA in EGFR (5.7%) and ERBB2 (7.9%), at 12.0%, across all tumor types, FGFR2 mut cancers may have higher frequency of TMB ≥ 20 mut/Mb suggesting potential immunotherapy responsiveness.

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