Early versus Late Onset Colorectal Cancer: Pathological Distinctions and Optimal Screening Age Determination in a Decade-Long Study

Background and Aim: The incidence of Early-Onset Colorectal Cancer (EOCRC) is increasing. However, the prognosis of EOCRC compared to Late-Onset Colorectal Cancer (LOCRC), and the ideal age for initial colorectal cancer (CRC) screening are not clear. In this study, we identified the pathological differences between the groups and determined the optimal screening age for CRC patients. Methods: We included 10,172 patients diagnosed with CRC from January 2011 to December 2021 in this study. Survival differences were compared by plotting Kaplan-Meier survival curves and conducting landmark analysis. Additionally, the diagnostic age of CRC patients was analyzed using age cumulative curves. Results : Compared to LOCRC patients, EOCRC patients had a higher proportion of defective mismatch repair (dMMR) and more advanced TNM staging (P < 0.05). The five-year survival of EOCRC patients was significantly better than that of LOCRC patients (P < 0.05). Laparoscopic surgery improved the long-term survival of EOCRC patients. Proficient mismatch repair (pMMR) favored the long-term survival of EOCRC patients. The survival rate of EOCRC patients at TNM stages I and II was higher than that of LOCRC patients at the same stages (P < 0.05). The age cumulative curve showed a substantial increase in the number of CRC patients at 40 years. Conclusion: The long-term prognosis of EOCRC patients is better than that of LOCRC patients, especially among those with pMMR, stages I-II, and who undergo laparoscopic surgery. For high-risk groups, the starting age for CRC screening should be 40 years.