Discussion on the Benefits of Postoperative Adjuvant Therapy for Stage II MSI-H Colorectal Cancer

Abstract

Background: There is no consensus among mainstream guidelines worldwide regarding adjuvant therapy for colorectal cancer patients with stage II microsatellite instability (MSI-H)/mismatch repair deficiency (dMMR) after surgery. This study aims to further explore the benefits of postoperative adjuvant chemotherapy for this group of patients through a retrospective study and assist in guiding clinical decision-making for this group of patients.

Methods: Finally a total of 140 patients with colorectal cancer who underwent radical surgery at the First Affiliated Hospital of Chongqing Medical University from January 2018 to December 2022, with postoperative pathological stage II (T3-T4N0M0) and molecular test results of MSI-H were retrospectively collected. Disease-free survival (DFS) and overall survival (OS) were recorded through outpatient and telephone follow-ups. The Kaplan-Meier method was used to calculate DFS and OS, and the logrank method was used for significance testing; Univariate and the multivariate Cox proportional hazards model were used to analyze prognostic factors.

Results: There were differences in age groups between the chemotherapy group and the non-chemotherapy group (adjuvant therapy acceptance rate in patients under 65 years old: 68.2% vs 25.0%, P< 0.01), but no significant differences in the remaining clinical data and pathological features (P > 0.05). Median survival was 49.2 months (3.3-89.1 months), and 3-year DFS and OS were 90.0% and 93.6%, respectively; The DFS (p=0.011) and OS (p=0.022) in the postoperative chemotherapy group were significantly prolonged. Univariate Cox regression analysis showed that the high-risk features including age > 65 years, no adjuvant chemotherapy, lymph node dissection < 12 were associated with poorer prognostic.

Conclusion: Postoperative adjuvant chemotherapy based on oxaliplatin in patients with stage II MSI-H colorectal cancer prolongs DFS and OS.