EP181 - High-Risk Features and Survival Outcomes in Stage II MSI-H Colorectal Cancer: A Retrospective Single-Centre Study

Purpose/Background: Stage II MSI-H colorectal cancer is generally associated with a favorable prognosis. However, certain high-risk features may portend inferior outcomes.

Methods/Interventions: This was a single-center retrospective study conducted at Taichung Veterans General Hospital, including patients diagnosed with stage II MSI-H colorectal cancer between 2016 and 2023. Categorical variables were compared using Chi-square test or Fisher’s exact test, and survival analyses were performed using Cox proportional hazards regression models to identify independent prognostic factors.

Results/Outcomes: Patients in the high-risk group exhibited inferior survival compared with low-risk patients (3-year OS: 86.0% vs. 96.0%, log-rank p=0.079). For PFS, survival rates were similar between patients receiving adjuvant chemotherapy (ACT) and those without (3-year PFS: 85.4% vs. 86.4%, log-rank p=0.894). Although T4 disease and obstruction did not reach statistical significance in Cox regression, survival curves consistently showed poorer OS and PFS in these subgroups.

Conclusion/Discussion: T4 tumor stage and bowel obstruction are associated with poorer prognosis in stage II MSI-H colorectal cancer. These findings suggest that patients with such high-risk features may warrant consideration of adjuvant therapy, despite the generally favorable outcomes associated with MSI-H tumors.

multivariable regression of 3-year overall survival rate