Abstract 1612: Molecular analysis of clinically actionable gene alterations in clear cell carcinoma of the ovary using next-generation sequencing and immunohistochemical CNV analysis

Abstract

Abstract Background: Ovarian clear cell carcinoma (OCCC) is more prevalent in Japan than western countries, exhibits chemoresistant phenotype and poor survival. Although several mutations in OCCC have been reported, sensitive and rapid detection about actionable gene alterations in formalin-fixed-paraffin embedded (FFPE) tissue is required for clinical usage. In this study, we aimed to investigate major eight actionable mutations using next-generaion sequencing (NGS), and CNV-associated overexpression and phosphorylation related to their pathway using immunohistochemistry (IHC) in OCCC. Methods: Sixty-nine consecutive patients diagnosed of OCCC in our hospital were included. SNV analyses of FFPE tissues from the primary lesions were investigated using the newly-developed GeneReader NGS platform and the Actionable Insight Tumour Panel (Qiagen) with high availability to old FFPE sample, and IHC was performed using tissue microarray (TMA). Results: Median (range) follow-up period was 46 (0-270) months. In FIGO2014 system, 43 patients (62%) were in stage I, 3 (4%) in stage II, 19 (28%) in stage III, and 4 (6%) in stage IV. Genomic DNAs could be extracted and be analyzed in NGS from 61 FFPE specimens (88%), of which median storage period was 116 (22-269) months. Somatic gene mutations were detected in seven genes of 40/61 patients; PIK3CA, 33 (54%); KRAS, 12 (20%); ERBB3, 4 (6.6%); EGFR, 4 (6.6%); BRAF, 3 (4.9%); RAF1, 1 (1.6%); ERBB2, 1 (1.6%). In comparison with Cosmic database and previous reports, PIK3CA, KRAS and BRAF mutation were detected more frequently in our cohort, that may be associated with higher performance of our deep sequencing, or with racial features of Japanese OCCC population. PIK3CA mutation was not correlated with prognosis in overall survival (OS), progression-free survival (PFS) and OS after recurrence. However, in the patients with KRAS mutation, median OS after recurrence was 5.5 months, which was significantly worse than that without the mutation (31 months, p value = 0.0274), although OS and PFS were not significantly different. KRAS mutation was positively correlated with MET, HER2 and HER3 overexpression and AKT phosphorylation in IHC. Conclusion: We could more frequently detect several actionable gene mutations even in old FFPE specimens, which may warrant the use of deep sequencing analysis about actionable gene mutations. Citation Format: Hiroshi Asano, Yutaka Hatanaka, Kanako C. Hatanaka, Asami Okumura, Toraji Amano, Takashi Mitamura, Tatsuya Kato, Yosuke Konno, Daisuke Endo, Kei Ihira, Ayako Nozaki, Yoshihiro Matsuno, Hidemichi Watari, Noriaki Sakuragi. Molecular analysis of clinically actionable gene alterations in clear cell carcinoma of the ovary using next-generation sequencing and immunohistochemical CNV analysis [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 1612.