Abstract 2305: Plant-based diets and subsequent risk of gastrointestinal cancers in Black and low-income Americans: Findings from a large prospective cohort study

Abstract Background: Plant-based diets have been promoted for their health benefits. However, no study has specifically evaluated plant-based diets in relation to risk of gastrointestinal cancers in Black and low-income populations who disproportionately experience poor health outcomes. We aimed to investigate associations of plant-based dietary patterns with incident colorectal, liver, and pancreatic cancers in 70,255 participants of the Southern Community Cohort Study, a population-based prospective cohort conducted among predominantly Black and low-income Americans. Methods: At baseline (2002-2009), dietary intakes were collected by a validated food frequency questionnaire from which adherences to overall, healthy, and unhealthy plant-based diets were assessed using established indices (i.e., PDI, hPDI, and uPDI). Incident cancer cases were ascertained via linkage to state cancer registries and the National Death Index. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated from Cox proportional hazards models after adjusting for potential confounders. In a subset of participants, we also examined associations of the three indices with shotgun metagenomic sequencing-profiled gut microbiome from stool samples (n=417) collected between 2018-2021 and mass spectrometry-measured metabolites from baseline plasma samples (n=1,581). Cancer cases diagnosed before stool or blood collection were excluded. Results: During a median follow-up time of 12.6 years, 544, 370, and 276 incident primary colorectal, liver, and pancreatic cancer cases were identified after excluding participants with less than 2 years of follow-up. Compared with the lowest quartile, the highest quartile of PDI was associated with lower colorectal cancer (CRC) risk (HR=0.72, 95% CI=0.55-0.94, Ptrend=0.01), whereas that of uPDI was associated with elevated CRC risk (HR=1.41, 95% CI=1.07-1.86, Ptrend=0.02). A high hPDI was linked to reduced liver cancer risk (HR=0.60, 95% CI=0.42-0.87 for the highest versus lowest quartile, Ptrend=0.006). No index was associated with pancreatic cancer risk. After adjusting for multiple testing (FDR-adjusted P<0.10), PDI was inversely associated with species MGYG-HGUT.02013 within genus Collinsella. PDI, hPDI, and uPDI were associated with 201, 107, and 47 circulating metabolites, respectively. Over-representation analysis suggested that caffeine and branched-chain amino acids metabolism pathways were significantly enriched for PDI-associated metabolites. Conclusion: Adherence to a diet characterized by healthy plant foods and low animal foods may lower colorectal and liver cancer risk. Citation Format: Fangcheng Yuan, Lei Wang, Danxia Yu, Wei Zheng. Plant-based diets and subsequent risk of gastrointestinal cancers in Black and low-income Americans: Findings from a large prospective cohort study. [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 2305.