Background. Composite Dietary Antioxidant Index (CDAI) is a summary score derived from statistical modeling that ranks an individual’s dietary intake of antioxidants in relation to the overall mean of the study population. Antioxidants may offer a beneficial effect on reducing the risk of pancreatic cancer. No prospective epidemiological study has investigated the association between food-based CDAI (fCDAI) and pancreatic cancer risk. Methods. The fCDAI score was calculated based on dietary intakes of vitamins A, C, and E, manganese, selenium, and zinc from food but not from dietary supplements, for each participant of the Singapore Chinese Health Study, a population-based prospective epidemiological cohort study consisting of 61,321 Chinese men and women in Singapore aged 45-74 years at baseline enrollment during 1993-1998. Intake of antioxidants was derived from self-reported consumption of food items using a validated semi-quantitative food frequency questionnaire and the Singapore Food Composition Table. Incident cases of cancer, including pancreatic cancer, and death were identified through the linkage analysis with the nationwide Singapore Cancer Registry and the Singapore Registry of Birth and Death, respectively. The Cox proportional hazard regression method was used to estimate hazard ratio (HR) and its 95% confidence interval (CI) of pancreatic cancer associated with higher quartiles of fCDAI relative to the lowest quartile with adjustment for multiple potential confounders, including age, sex, dialect group, level of education, smoking status, alcohol consumption, a history of diabetes, sleep duration, physical activity, year of enrollment, and total energy intake. Results. Overall, 311 participants who were free of cancer at baseline developed pancreatic cancer during an average of 17.7 years of follow-up after baseline assessment of food consumption. Compared with the lowest quartile, the multivariable-adjusted HR of pancreatic cancer for the highest quartile of fCDAI was 0.54 (95% CI: 0.31-.91, P=0.02). This inverse association between the fCDAI and pancreatic cancer risk was more apparent in overweight/obese subjects (HRQ4vsQ1=0.28, 95% CI: 0.13-0.60, Ptrend=0.02), or those without a history of diabetes (HRQ4vsQ1=0.50, 95% CI: 0.29-0.88, Ptrend=0.04). No association was observed between CDAI derived from dietary supplements and the risk of pancreatic cancer. Conclusions. The inverse association between fCDAI and pancreatic cancer risk supports the notion that overall dietary antioxidants may provide a beneficial effect against the development of pancreatic cancer, specifically overweight/obese individuals and those free of diabetes who may have a long-term persistent dietary pattern. These results highlight the importance of promoting healthy eating for the primary prevention of pancreatic cancer. Citation Format: Pedram Paragomi, Renwei Wang, Aizhen Jin, Yi-Chuan Yu, Randall E. Brand, Li-Ting Sheng, An Pan, Woon-Puay Koh, Jian-Min Yuan, Hung Luu. Composite dietary antioxidant index and the risk of pancreatic cancer: Findings from a prospective cohort study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3667.