Abstract B074: A biobank of fecal immunochemical tests (FIT) to study gut microbiome-mediated cancer disparities
Authors: Byrd Doratha , Hogue Stephanie , Wang Xuefeng , Forsyth Sugriva , Fuentes Martha , Egan Kathleen , Carson Tiffany , Kim Youngchul , Islam Jessica , Meade Cathy , Gwede Clement 
Published: December 2023

Introduction: Colorectal cancer (CRC) poses a disproportionate burden among certain Hispanic/Latino subgroups, such as Puerto Rican and Cuban individuals, and Black individuals. Causes of CRC disparities are poorly understood but are likely driven by social determinants of health (SDOH), which may directly and indirectly influence the gut microbiome (GM). In turn, the GM is increasingly implicated in colorectal carcinogenesis. Therefore, it is plausible that the GM may be targeted to reduce excess CRC burden among disproportionately affected populations. However, prior studies of the GM and CRC had limited inclusion of underserved populations and limited collection of SDOH data. Objective: To clearly define the role of the GM in CRC and other cancer disparities, we conducted a pilot study to establish a well-annotated cohort that includes longitudinally collected fecal specimens among diverse populations. Methods: We leveraged fecal immunochemical tests (FIT), a cost-effective method for CRC screening in patient populations with limited access to colonoscopy, in which the GM can be well characterized. Participants completed annual FIT testing following standard protocols as implemented in a Federally Qualified Health Center. FIT samples were processed and banked at Moffitt Cancer Center in -80ºC freezers. All participants completed stool and risk factor questionnaires capturing SDOH, medical history, diet, and lifestyle exposures. To further validate the FIT microbiome, we extracted DNA from 8 sets of triplicate FIT aliquots (200ul each) using the automated MagCore®️ DNA Kit and then performed shotgun sequencing to characterize the fecal microbiome. To test for quality of the data and to compare microbiome metrics (e.g., alpha diversity and microbial abundances) in replicate samples, we calculated intraclass correlation coefficients (ICCs) using linear mixed effects models. Results: In just one clinic, to date, more than N=79 individuals who are primarily Spanish speakers and persons from other racial/ethnic minority subgroups have been enrolled. The racial and ethnic distribution included 39% Mexican, 11% Black, 6% Puerto Rican, 9% Central or South American, and 5% Cuban individuals. Approximately, 59% of the consented population preferentially spoke Spanish and 14% tested positive on the FIT. In the pilot FIT testing samples, we found that the integrity of the DNA was high, with only a few (N=3 of 24) samples with insufficient DNA yield for shotgun metagenomic sequencing. ICCs were generally above ≥ 95% for alpha diversity metrics and abundance of species/genes indicating excellent handling and processing procedures for FIT microbiome extraction and sequencing. Conclusion: Our findings support the concept that FIT-based community screening programs offer exceptional opportunity for GM research in diverse, underrepresented populations. Our future studies will integrate the SDOH data and expand this cohort with the goal of contributing novel insights regarding associations of the GM with early pathogenesis of CRC across diverse populations. 

Citation Format: Doratha Byrd, Stephanie Hogue, Xuefeng Wang, Sugriva Forsyth, Martha Fuentes, Kathleen Egan, Tiffany Carson, Youngchul Kim, Jessica Islam, Cathy Meade, Clement Gwede. A biobank of fecal immunochemical tests (FIT) to study gut microbiome-mediated cancer disparities [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B074.