Abstract B211: Comparison of detection of FGFR2 amplification by quantitative real-time-PCR (qPCR) and fluorescent in situ hybridization (FISH) in gastric cancer.

Abstract

Abstract Background: Fibroblast growth factor receptor 2 (FGFR2) amplification is associated with tumorigenesis of gastric cancer and can be a promising molecular target for the treatment of FGFR2-amplified gastric cancer. So far, the most optimal single method to screen patients with FGFR2 amplification has not been determined. To screen patients with gastric cancer harboring FGFR2 amplification, we aim to investigate whether qPCR can replace the FISH method which is the golden standard but less sensitive and much more expensive than qPCR. Methods: FISH (Abnova, #FG0018) and qPCR (Applied Biosystems, HS05182482_cn) method for FGFR2 amplification were performed with formalin-fixed paraffin-embedded (FFPE) tissues of patients with gastric cancer who were diagnosed from 2007 to 2012 in Asan Medical Center, Seoul, Korea, and whose FFPE tissues contained at least 70% of tumor cells. qPCR was conducted initially in 26 patients who had both endoscopic biopsy and surgical tissues in the diagnosis to figure out which samples are better between biopsy and surgical tissues. According to the results, 182 patients with endoscopic biopsy tissues were further included. FISH was defined as positive in case of FGFR2 to CEP10 ratio > 2.0. Results: In 26 patients who had paired endoscopic biopsy and surgical samples, the qPCR-based copy number assay for FGFR2 amplification was more sensitive in biopsy samples; i.e., FGFR2 copy number by qPCR was higher in biopsy samples in 13 (50%) patients, while it was higher in surgical samples only in 3 (11.5%) patients. In a total of 208 endoscopic biopsy FFPE samples including 182 patients with biopsy tissues, copy number of FGFR2 ranged from 0.8 to 399.0 (median 15.9) by qPCR and from 0.7 to 166.9 (median 6.1) by FISH. 16 biopsy samples showing FGFR2 copy number > 10 by qPCR were all FISH-positive, while 192 biopsy samples showing FGFR2 copy number < 10 by qPCR were all FISH-negative. In cases of FGFR2 copy number > 10 in biopsy tissues by qPCR, the copy numbers were very well correlated between qPCR and FISH in all patients, and were also over 10 in surgical tissues regardless of methods in 26 patients. The positive rate of FGFR2 amplification was 7.7% with a cut-off value of 10 by qPCR. Conclusion: This study suggests that it is better to use biopsy samples than surgical tissues to detect FGFR2 amplification by qPCR; and for patient screening in gastric cancer, the optimal cut-off value for definite FGFR2 amplification by qPCR is 10 in comparison with the results of FISH. Clinical relevance of intermediate FGFR2 copy number elevation < 10 by qPCR needs to be addressed in future clinical trials using FGFR2 inhibitors. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B211. Citation Format: Young-Soon Na, Young Soo Park, Min-Hee Ryu, Chae-Won Lee, Hye Jin Park, Ju-Kyung Lee, Sook Ryun Park, Baek-Yeol Ryoo, Yoon-Koo Kang. Comparison of detection of FGFR2 amplification by quantitative real-time-PCR (qPCR) and fluorescent in situ hybridization (FISH) in gastric cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B211.