Abstract 2197: Weight history and colorectal cancer risk in the Cancer Prevention Study-3 cohort
Authors: Um Caroline Y. , Newton Christina C. , Parikh Aparna , McCullough Marjorie L. , Patel Alpa V. 
Published: March 2024

Abstract
While the link between obesity and colorectal carcinogenesis is established, limited evidence suggests that early-life overweight/obesity may be an important consideration, particularly in the development of early-onset colorectal cancer (CRC). Using data from the American Cancer Society’s Cancer Prevention Study-3 (CPS-3), we investigated the association of body weight across the life course and risk of CRC.
From 2006-13, over 300,000 participants (ages 30-65) enrolled in the CPS-3 cohort and provided a baseline waist circumference (WC) measure, self-reported baseline weight and height, weight at age 18, and weight at each decade of adulthood (20s to current age). Body shape phenotype (apple, pear, other) was self-reported in 2015. Excess body mass index (BMI)-years was calculated by subtracting a reference BMI of 25 from the reported BMI for each decade of life and aggregating excess BMI for the reported years of life. Through 2018, 424 incident cases of colorectal cancer were reported, of which 94 were younger than 50 years. Associations of BMI measures and WC with incident CRC were estimated using multivariable-adjusted Cox proportional hazards regression and stratified by sex and body shape.
After exclusions (n=248,804), 78% of participants were women, 85% were non-Hispanic white, 69% were never smokers, and 8% had a family history of CRC. The mean baseline age was 47.8 (women) and 48.5 (men) years. The mean baseline BMI, WC, and age 18 BMI were 27.6 kg/m2, 91.9 cm, and 21.7 kg/m2, respectively, among women and 28.3 kg/m2, 103.8 cm, and 23.1 kg/m2, respectively, among men. Baseline BMI was associated with 8% higher CRC risk (95% confidence interval (CI) 0.99-1.18) per 5 kg/m2 increase. However, apple body shape was associated with higher CRC risk (hazard ratio (HR) per 5 kg/m2 BMI = 1.18, 95% CI 1.02-1.38). WC was associated with higher CRC risk (HR 1.08, 95% CI 1.01-1.15) per 10 cm increase, and the association was higher for apple body shape (HR 1.14, 95% CI 1.01-1.28). BMI at age 18 was associated with 17% higher CRC risk (95% CI 1.03-1.32) per 5 kg/m2 increase, and the association was higher for apple body shape (HR 1.36, 95% CI 1.12-1.65). Associations for non-apple body shapes were not statistically significant across all exposures. For early-onset CRC, associations with baseline BMI, WC, and age 18 BMI were suggestive of higher risk but not statistically significant. Participants in the highest category of excess BMI-years (women ≥35, men ≥81) relative to those in the lowest had 56% higher risk of overall CRC (95% CI 1.19-2.05), but the association with early-onset CRC was not statistically significant (HR 1.92, 95% CI 0.90-4.07).
These findings suggest that while obesity is associated with higher CRC risk, excess weight gain around the waist and at younger ages may be of importance. Studies are needed to confirm these findings and further investigate the potential role of early-life obesity in the development of early-onset CRC.
Citation Format: Caroline Y. Um, Christina C. Newton, Aparna Parikh, Marjorie L. McCullough, Alpa V. Patel. Weight history and colorectal cancer risk in the Cancer Prevention Study-3 cohort [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 2197.