Abstract 3467: Tumor immune and microbial characteristics of colorectal cancer according to age at diagnosis and detailed anatomical location

Abstract Background: Colorectal cancer is a heterogeneous disease, exhibiting spectra of tumor characteristics that vary across age at diagnosis and anatomical location. We hypothesized that tumor immune and microbial characteristics of colorectal cancer might change with age at diagnosis and detailed anatomical location. Methods: We utilized a pooled dataset of colorectal cancer cases (N= 958 to1413 depending on variables) with available immune cell density or microbial data in the Nurses' Health Study, Health Professionals Follow-up Study, and Ontario Familial Colon Cancer Registry. We examined whether there were statistically significant trends in tumor immune and microbial according to age at diagnosis and detailed primary tumor location (cecum, ascending, hepatic flexure, transverse, splenic flexure, descending, sigmoid, rectosigmoid, rectum) using Spearman’s correlation test. The densities of immune cells were determined by using multiplex immunofluorescence, including T cells (CD3, CD4, CD8, CD45RA, CD45RO, FOXP3) and macrophages (CD68, M1-like, and M2-like) in tumor intraepithelial and stromal regions. We conducted stratified analyses by microsatellite instability (MSI) status. Results: The density of memory (both CD4+ and CD8+) T cells in tumor epithelial areas continuously increased as age at diagnosis increased (P for trend <0.005). Compared to later-onset colorectal cancer, early-onset colorectal cancer had a lower density of memory T-cells. With respect to tumor site, CD3+CD4+ and CD3+CD8+ T densities in tumor epithelial areas were highest in the cecum compared to other subsites, and there was a statistically significant decreasing trend from the cecum to rectum (P for trend <0.005). We also observed significant decreasing trends for CD68+, M1-like, and M2-like macrophage densities in combined tumor (intraepithelial and stromal) regions from the cecum to rectum (P for trend <0.005). The proportion of F. nucleatum-positive colorectal cancers gradually decreased from the cecum to rectum (P for trend <0.005). Similar trends were observed in separate analyses in non-MSI-high cases. Conclusions: This study suggests that certain tumor immune and microbial characteristics in the tumor microenvironment, specifically T cell and macrophage densities and Fusobacterium nucleatum positivity, change gradually according to age at diagnosis and/or detailed anatomical location. Age and anatomical location spectra in tumor immune and microbial characteristics will shed light on the etiology of colorectal cancer (including early-onset colorectal cancer), leading to better-personalized cancer prevention and treatment. Citation Format: Tomotaka Ugai, Yasutoshi Takashima, Yuxue Zhong, Juha P. Väyrynen, Daniel Buchanan, Jeroen Huyghe, Li Hsu, Conghui Qu, Sushma Thomas, Claire Thomas, Steve Gallinger, Robert Grant, Ulrike Peters, Amanda I. Phipps, Jonathan Nowak, Shuji Ogino. Tumor immune and microbial characteristics of colorectal cancer according to age at diagnosis and detailed anatomical location [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 3467.