Abstract 2510: Clinicopathologic significance of fibroblast growth factor 2 type IIIb and type IIIc in gastric cancer

[Background]Fibroblast Growth Factor Receptor 2(FGFR2) amplification occuers flequently in undifferentiated gastric cancer(GC), and accounts for 3-10% of primay GC. FGFR2 shows two isoforms, IIIb-type expressed in epithelial cells, and IIIc-type expressed in mesenchymal cells. The aim of this study is evaluating clinicopathological significance of FGFR2-IIIb and IIIc expression on GC cells. [Method]562 patients who had undergone GC surgery were retrospectively examined. Immunohistochemistry of resected specimen was used to investigate the expression of FGFR2-IIIb and IIIc. [Result]FGFR2-IIIb and FGFR2-IIIc were positive in 28 cases (4.9%) and 4 cases (0.7%) of 562 gastric cancers. All of FGFR2-IIIc positive tumors were also positive for FGFR2-IIIb in a same tumor, but both were not positive in same cells. 5-year overall survival rate of FGFR2 positive group is significantly poorer (p=0.0011, log-lank) than that of FGFR2 negative. Moreover, the prognosis of FGFR2-IIIc positive group was significantly poorer (p=0.003, log-lank) than that of FGFR2-IIIb positive group. In univariate analysis, the overall survival was significantly correlated to FGFR2-IIIb positive, FGFR2-IIIc positive, invasion depth, macroscopic type, histological type, lymph node metastasis, peritoneal dissemination, lymphatic invasion, and cytology. In multivariate analysis, FGFR2IIIc was significantly correlated to overall survival (p=0.045) [Conclusion] The expression of FGFR2IIIc and/or FGFR2IIIb was observed in 5% of gastric cancer. FGFR2 amplification is associated with poor overall survival. As a result, treatment targeting FGFR2 amplification has the potential to provide clinical benefit for FGFR2 positive GC. Citation Format: Kenji Kuroda, Masakazu Yashiro, Go Masuda, Yuichiro Miki, Tomohisa Okuno, Shingo Togano, Takahiro Toyokawa, Hiroaki Tanaka, Kazuya Muguruma, Kosei Hirakawa, Masaichi Ohira. Clinicopathologic significance of fibroblast growth factor 2 type IIIb and type IIIc in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2510.