Simple SummaryColorectal cancer is increasingly recognized as two separate diseases: colon cancer and rectal cancer, each with its own causes and outcomes. We included 674 patients with colorectal cancer, with pre-surgery collected blood samples, and patient follow up for an average of 4.4 years. Ninety-three patients (14%) died from various causes including 60 patients with colon cancer and 33 patients with rectal cancer. Higher levels of plasma creatinine increased the risk of death by 39% in patients with rectal but not colon cancer. We further identified a biological pathway (e.g., roadmaps inside our bodies that guide various processes) related to starch and sucrose metabolism, which was linked to worse clinical outcomes in colon cancer but not rectal cancer. There is some evidence, that resistant starch, which resists digestion in the small intestine, may offer protection against colon cancer. Understanding the distinct causes and outcomes of colon and rectal cancer is crucial for tailoring effective treatments. In conclusion, personalized treatment strategies should consider colon cancer and rectal cancer separately and are essential for improving patient outcomes in the future.AbstractColorectal cancer (CRC) is increasingly recognized as a heterogeneous disease. No studies have prospectively examined associations of blood metabolite concentrations with all-cause mortality in patients with colon and rectal cancer separately. Targeted metabolomics (Biocrates AbsoluteIDQp180) and pathway analyses (MetaboAnalyst 4.0) were performed on pre-surgery collected plasma from 674 patients with non-metastasized (stage I–III) colon (n= 394) or rectal cancer (n= 283). Metabolomics data and covariate information were received from the international cohort consortium MetaboCCC. Cox proportional hazards models were computed to investigate associations of 148 metabolite levels with all-cause mortality adjusted for age, sex, tumor stage, tumor site (whenever applicable), and cohort; the false discovery rate (FDR) was used to account for multiple testing. A total of 93 patients (14%) were deceased after an average follow-up time of 4.4 years (60 patients with colon cancer and 33 patients with rectal cancer). After FDR adjustment, higher plasma creatinine was associated with a 39% increase in all-cause mortality in patients with rectal cancer. HR: 1.39, 95% CI 1.23–1.72, pFDR= 0.03; but not colon cancer: pFDR= 0.96. Creatinine is a breakdown product of creatine phosphate in muscle and may reflect changes in skeletal muscle mass. The starch and sucrose metabolisms were associated with increased all-cause mortality in colon cancer but not in rectal cancer. Genes in the starch and sucrose metabolism pathways were previously linked to worse clinical outcomes in CRC. In summary, our findings support the hypothesis that colon and rectal cancer have different etiological and clinical outcomes that need to be considered for targeted treatments.