Abstract 1146: Identification of genetic mutations using circulating tumor cells, circulating tumor DNA, and exosomes in patients with colorectal cancer

Abstract Introduction: Circulating tumor cells (CTCs) are expected to provide various types of information about tumors. However, their low abundance in the bloodstream poses a challenge to obtaining a sufficient quantity for analysis. For detecting genetic mutations, circulating tumor DNA (ctDNA) has higher sensitivity. We previously reported that the sensitivity of detecting RAS mutation using ELESTA CROSSORTER (AFI Technology) is only 10.3%. Thus, we improved our system to enhance the sensitivity of detecting gene mutations using CTC, and compared the gene identification sensitivity of CTCs with identification sensitivities using ctDNA and exosomes through a novel method. Methods: This study included patients with RAS-mutant colorectal cancer. CTCs were isolated using the ELESTA CROSSORTER. This device removes red blood cells and impurities through size-based separation via a unique microfluidic channel and isolates CTCs from white blood cells and dead cells using electrical property-based separation. RAS mutations in DNA extracted from CTCs, exosomes, and ctDNA were identified using droplet digital PCR. Results: The study included 22 patients (1 with Stage I, 4 with Stage II, 7 with Stage III, and 10 with Stage IV colorectal cancer). RAS mutations were detected in 7 cases (31.8%) using CTCs, in 10 cases (45.5%) using ctDNA, and in 6 cases (27.3%) using exosomes. RAS mutations were identified exclusively by CTCs in 2 cases, exclusively by ctDNA in 3 cases, and exclusively by exosomes in none. In 3 cases, mutations were identified by all three methods. Among patients with Stage III and IV colorectal cancer, 6 cases were detected using CTCs, 10 using ctDNA, and 6 using exosomes. No RAS mutations were identified exclusively by CTCs, while 3 cases were detected exclusively by ctDNA. Discussion: Through our recent improvements, the gene mutation detection sensitivity of CROSSORTER has been enhanced. These improvements include the following three key changes: switching the blood collection tube to a Streck tube, modifying the microfluidic channel to increase the white blood cell removal rate, and altering the liquid flowing through the channel to prevent clogging. As a result, the white blood cell removal rate has improved. However, we are continuing our efforts to achieve an even higher removal rate. Citation Format: Takeshi Yamada, Koki Hayashi, Kyoichi Oshiro, Kay Uehara, Shintaro Kanaka, Kohki Takeda, Ryo Ohta, Toshimitsu Miyasaka, Yasuyuki Yokoyama, Goro Takahashi, Takuma Iwai, Takanori Matsui, Seiichi Shinji, Akihisa Matsuda, Hiroshi Yoshida. Identification of genetic mutations using circulating tumor cells, circulating tumor DNA, and exosomes in patients with colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1146.