Abstract A16: The potential of circulating cell-free tumor DNA as a diagnostic marker of ovarian cancer

Abstract Objective: Circulating cell-free tumor DNA (ctDNA) is fragmented DNA released from cancer cells into the circulation. Technological development of digital PCR allows us to detect a small quantity of ctDNA in the circulation, suggesting its possibility for a future noninvasive biomarker. The aim of this study is to pursue its potential as a diagnostic biomarker to detect ovarian cancer using patients’ plasma. Methods: Twenty-five plasma samples from patients were collected before treatment. The corresponding tumors were also collected, and DNA was extracted. As nonmalignant controls, 10 samples were collected from patients with benign endometrial cysts. Three primers to detect PIK3CA mutations for endometriosis-related carcinoma and three primers to detect TP53 mutations for serous carcinoma were prepared. The presence of these mutations in ctDNA existing in patients’ plasma was confirmed with digital PCR method. PCR data were validated with tumor DNAs. Results: There were 7 cases of clear cell carcinoma,1 endometrioid carcinoma, and 7 serous carcinoma. Among 8 patients with endometriosis-related cancers (clear cell and endometrioid), PIK3CA mutations in plasma were detected in 6 cases, while mutations were not detected in benign endometrial cysts. Among 7 patients with high-grade serous carcinoma, TP53 mutations in patients’ plasma were detected in all cases. The presence of these mutations was confirmed by tumor DNAs. Conclusion: PIK3CA mutation in endometriosis-related cancer and p53 mutation in serous carcinoma were successfully detected in patients’ plasma, suggesting the potential of ctDNAs as a future noninvasive biomarker for ovarian cancer. Citation Format: Misa Yamamoto, Kenjiro Sawada, Aasa Shimizu, Yuri Matsumoto, Michiko Kodama, Kae Hashimoto, Tadashi Kimura. The potential of circulating cell-free tumor DNA as a diagnostic marker of ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A16.