Abstract 6683: The abundance of Fusobacteria nucleatum in tumor tissue is a prognostic factor in patients of right-sided colorectal cancer

Abstract Background: A significant association between the gut microbiome and colorectal carcinogenesis, as well as cancer progression. It has been reported that Fusobacteria nucleatum (F. nucleatum) is one of the most famous bacteria associated with colorectal cancer (CRC). It has been reported that the abundance of F. nucleatum is associated with colorectal cancer-specific survival (CSS), however it remains unclear for association with F. nulceatum and relapse-free survival (RFS). If F. nucleatum has a significant involvement in tumor progression of colorectal cancer, the abundance of F. nucleatum should be associated with not only CSS but also RFS in colorectal cancer. In this study, we measured the bacterial mass of F. nucleatum in tumor tissue of CRC patients in Stage II-III to explore the differences in prognosis. Methods: We included patients with CRC in stage II-III who underwent surgical treatment at Nippon Medical School Hospital between January 2017 and December 2020 except patients who received preoperative chemoradiotherapy and had multiple cancers. We measured the absolute of F. nucleatum copy number of the DNA exacted tumor tissues using droplet digital PCR. Results: 253 patients with CRC were included. 128 patients had pathological stage II and 125 patients had pathological stage III. Among 253 patients, 104 patients had right-sided CRC, 89 patients had left-sided, and 60 patients had rectal cancer. F. nucleatum was detected in 166 patients (65.6%), and the median of F. nucleatum copy number was 1.08 (range; 0.00 -2791.3). F. nucleatum copy number was more abundant in right-sided CRC than in left-sided and rectal cancer (p= 0.02, p=0.01). There was no significant difference between stage II CRC and stage III. We categorized patients into two groups based on the median cut point of F. nucleatum copy number: the F. nucleatum-high group and the F. nucleatum-low group for comparison with clinicopathological features and prognosis. Patients with high abundance of F. nucleatum exhibited T4 of tumor depth (p=0.03), right-sided CRC (p=0.01), longer tumor circumference (p <0.001), longer tumor length (p <0.001), and no lymph node metastasis (p=0.024). There was no significant difference in relapse-free survival between the F. nucleatum-high group and F. nucleatum-low group among whole patients (p=0.53). Analyzing divided tumor location, in right-sided CRC high abundance of F. nucleatum was significantly associated with shorter relapse-free survival than low abundance (p=0.02), while in left-sided and rectal cancer there was no significant difference (p=0.61). Conclusion: F. nucleatum was more abundant in right-sided CRC and associated with relapse-free survival only in right-sided CRC. F. nucleatum may make a greater impact on right-sided CRC than on left-sided and rectal cancer. Citation Format: Toshimitsu Miyasaka, Takeshi Yamada, Sho Kuriyama, Akihisa Matsuda, Kay Uehara, Seiichi Shinji, Yasuyuki Yokoyama, Goro Takahashi, Takuma Iwai, Kohki Takeda, Shintaro Kanaka, Hiroshi Yoshida. The abundance of Fusobacteria nucleatum in tumor tissue is a prognostic factor in patients of right-sided colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6683.