Metabolomic differences in young-onset versus average-onset colorectal adenocarcinoma.

3510 Background: Novel deleterious effects of environmental exposures may play a role in the rising incidence of young-onset colorectal cancer (yoCRC). We used metabolomics to assess differences between yoCRC and average-onset CRC (aoCRC), in comparison to healthy controls, which may provide insight into the pathogenesis and suggest any exposure risks. Methods: Patients with stage I-IV CRC and healthy controls were identified from prospective biobanks and categorized based on age < 50 years (yoCRC or young controls) or age > 60 years (aoCRC or older controls). Plasma metabolites were profiled using GC-TOF mass spectrometry. Differential abundance of metabolites was investigated using unadjusted and adjusted logistic regression. Metabolic pathway analysis was performed using Metaboanalyst 5.0. All p-values were adjusted for multiple testing (false-discovery rate, FDR p < 0.20 considered significant). Results: The study population comprised 170 CRC patients (66 yoCRC and 104 aoCRC) and 49 healthy controls (34 young and 15 old). Association analyses revealed four differentially abundant metabolites: citrate (FDR p = 0.04), cholesterol (0.14), and two unidentified metabolites (UM). Metabolic pathways significantly altered in yoCRC vs. aoCRC included: carbohydrate metabolism (citrate cycle, FDR p = 0.04), carbohydrate biosynthesis (glyoxylate and dicarboxylate metabolism, FDR p = 0.004), amino-acid metabolism (alanine, aspartate, and glutamate metabolism, FDR p = 0.01, arginine biosynthesis, FDR p = 0.02, and amino-acid t-RNA biosynthesis, FDR p = 0.03). There were no significant metabolomic differences between young and old controls. Significant associations on survival analysis included: adipic acid with aoCRC (HR = 3.1, 95% CI = , 1.7-5.6, FDR p = 0.13, unadjusted analysis) suggesting worse survival with higher levels and 4-hydroxyhippuric acid with the whole cohort (HR = 0.4, 95% CI = 0.3-0.7, FDR p = 0.05, adjusted analyses) indicating better survival with higher levels. Conclusions: We identified significant differences in the citrate cycle - a core pathway of cellular metabolism associated with colorectal cancer. Metabolomic differences in pathways of carcinogenic significance (aspartate) and environmental exposures (arginine and dietary red meat) were also noted, suggesting potential relationships with younger age of CRC onset. [Table: see text]