Abstract NG09: A biobank of Fecal Immunochemical Tests (FIT) for gut microbiome measurement: A paradigm for studying the microbiome and cancer
Authors: Byrd Doratha A. 
Published: April 2023

Abstract
The broad and long-term goal of this study is to support the biobanking of fecal samples for development of prospective microbiome cohorts in large and diverse study populations. The gut microbiome, comprising trillions of microbes residing in the gut, is involved in the etiology of multiple health conditions, with emerging evidence for a role in cancer. Establishing a role for the microbiome in cancer risk has been difficult since, at present, availability of pre-diagnostic fecal specimens is severely limited in existing cohorts to study prospective microbiome-cancer associations. To advance knowledge in the field, it is critical to establish prospective microbiome cohorts that include samples from diverse study populations. Mounting evidence supports that the collective activity of the gut microbiota may influence development and progression of colorectal cancer (CRC), the second overall leading cause of cancer death in the United States. There are persistent CRC disparities in the US-with African Americans and those living in rural areas suffering higher CRC incidence and mortality. Explanations for CRC disparities are likely multifactorial, involving differences in lifestyle, socioeconomic, social, and other environmental exposures. These exposures likely act individually and interact to affect gut microbiome composition, resulting in the variation of microbiome-CRC associations across race/ethnicity and geographic location. Yet, microbiome-mediated mechanisms for CRC disparities remain largely unstudied. To advance knowledge in the field, future microbiome studies should encompass diverse study populations, include those with limited access to direct-to-colonoscopy screening, and collect detailed data on targetable exposures that alter the microbiome and drive CRC disparities. Moffitt Cancer Center is presently implementing multilevel, evidence-based CRC screening intervention programs aiming to expand access to CRC screening and improve screening rates in the community setting. These programs leverage fecal immunochemical tests (FIT), which are cost-effective and preferable for CRC screening in diverse patient populations without access to colonoscopy. Our preliminary data indicate that the fecal microbiome can be characterized in residual FIT samples using both 16S rRNA and metagenomic sequencing. The FIT microbial profiles were stable after multiple days at room temperature and were comparable to the field ‘gold-standard’. Therefore, CRC screening programs to improve FIT screening uptake provide ideal infrastructure to prospectively collect fecal specimens in diverse, unreached populations. Extending our findings of the suitability of FIT for microbiome assessment is a critical first step to move the field forward and to establish infrastructure for future population-based research on the microbiome and cancer disparities. As a speaker in a major session at AACR, I will describe our efforts to support large, multicenter grants that focus on establishing prospective microbiome and cancer cohorts. I will update the audience on our progress in completing the following specific aims:
Specific Aim 1: Implementing baseline and repeat collection and storage of residual FIT samples in community clinics in the Tampa Bay Area leveraging existing FIT screening infrastructure. Subjects complete FIT testing following standard protocols, and, after hemoglobin testing, the residual sample is processed and stored in -80°C freezers at Moffitt Cancer Center. Participants complete baseline questionnaires and data are linked to medical record and Florida cancer registry data for active prospective follow-up. We began our pilot study in a small, low-traffic clinic to establish our study workflow. We have recently expanded the study, recruiting N=37 participants. With continued expansion to larger clinics in the Tampa Bay Area, we estimate we will have recruited &gt; 100 participants by March 2023.
Specific Aim 2: To inform larger-scale studies,we will validate the use of FIT samples for investigating associations of the microbiome with colorectal neoplasms. To do this, we will pilot a shotgun metagenomic sequencing approach to characterize the fecal microbiome in residual FIT samples from Aim 1. We will sequence the metagenome among 1) those who tested positive on the FIT and subsequently were diagnosed with advanced adenoma, an established precursor to CRC, via colonoscopy (N=20); 2) those who tested negative on the FIT at baseline (N=20); and 3) those who tested negative on the FIT at baseline with a second negative FIT collected 2-years after baseline (N=20 repeat samples). Then, we will quantify the percentage of FIT samples successfully metagenomically sequenced, compare our microbiome-adenoma findings to previous fecal microbiome studies, and estimate stability of the FIT microbiome over 2 years.
Impact and future directions: We will demonstrate support for expanding collection and use of residual FIT samples as a practical, cost-effective approach for investigating associations of the microbiome with disease in diverse study populations. In the future, our biobank will serve as a distinctive resource to study prospective microbiome-disease associations. Future directions include additional pilot studies supporting the use FIT samples for microbiome research, establishing multicenter collaborations, and larger-scale investigations of prospective associations of the FIT microbiome with CRC.
Citation Format: Doratha A. Byrd. A biobank of Fecal Immunochemical Tests (FIT) for gut microbiome measurement: A paradigm for studying the microbiome and cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr NG09.