Background: Obesity may increase colorectal cancer (CRC) risk, primarily through mechanisms of increased inflammation. BMI is the most commonly used measure of adiposity; however, it may less accurately measure adiposity in Black populations, highlighting the need for biomarkers of inflammation to evaluate risk. Herein, we investigate the associations between BMI, albumin as a biomarker of inflammation, and CRC risk. Methods: Participant data arise from 71,141 participants of the Southern Community Cohort Study, of which 724 were diagnosed with incident CRC; 69% of the cohort are Black, and 56% have household income <$15,000. A subset of 277 cases and 642 controls had serum albumin concentration measured from blood samples taken at enrollment. Controls were selected through incidence density sampling of the cohort and individually matched to cases by age, sex, and race. Cox proportional hazards were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between BMI and CRC risk. Conditional logistic regression was used to calculate odds ratios (ORs) and 95%CIs for associations between albumin concentrations and CRC risk. WHO categories of BMI and albumin concentration tertiles determined through the control’s distribution were used. Results: Participants with underweight (<18.5) compared to normal (18.5-24.9) BMI had increased CRC risk (HR:1.69, 95%CI:0.95-2.98). Null associations were observed between overweight and obese BMI and CRC risk compared to normal BMI participants. Associations between BMI and CRC risk did not vary by sex or race (p-interactions>0.05). Albumin concentration was lower in Black participants and inversely associated with CRC risk (per-standard-deviation increase: OR:0.86, 95%CI:0.74,0.99). Associations were most apparent in participants who self-identified as Black race (OR 0.81, 95%CI:0.68,0.97), or female (OR:0.80, 95%CI:0.65,0.98). There was no evidence that albumin mediated the association between BMI and CRC risk, however BMI modified the association between albumin and CRC (BMI <30: OR: 0.90 95%CI:0.73,1.11; BMI ≥30: OR:0.75, 95%CI:0.60,0.95; p-interaction=0.07). Conclusions: Our results support the role of an inflammatory mechanism to increase CRC risk. The null associations between overweight and obese BMI with CRC risk displays the limited predictive utility of BMI in Black populations. Lower albumin concentrations and increased inflammation in Black populations, particularly in the presence of increased adiposity, may represent a contributing factor to racial disparity in CRC incidence.

Citation Format: Shaneda Warren Andersen, Zoe Walts, Ronni Brent, Lisa Parlato. Associations of BMI and albumin with colorectal cancer risk: A prospective cohort study [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr A006.