TPT 1.09 Mismatch Repair Deficiency and Postoperative Outcomes Following Colon Cancer Surgery

Abstract Background Mismatch repair deficiency (dMMR) defines biologically distinct subtype of colon cancer with recognised prognostic and therapeutic implications. However, its impact on postoperative morbidity and disease recurrence following colon cancer surgery remains unclear. Study aimed to evaluate the association between mismatch repair status and short- and long-term outcomes following curative colon cancer resection. Methods A retrospective cohort study was conducted including patients undergoing curative colon cancer resection between 2020 and 2023. Patients with non-metastatic disease and documented mismatch repair status were included and stratified into mismatch repair deficient (dMMR) and proficient mismatch repair (pMMR) groups. Primary outcomes were postoperative complications. Secondary outcomes included reoperation, hospital readmission, and disease recurrence within five years. Associations between mismatch repair status and outcomes were analysed using chi-square or Fisher’s exact tests as appropriate. Results A total of 238 patients undergoing curative colon cancer resection were included, of whom 50 (21.0%) had dMMR tumours. Overall postoperative complication rates were comparable between dMMR and pMMR patients (34.0% vs 28.2%, p=0.55). There were no significant differences in reoperation rates (12.0% vs 8.0%, p=0.55) or hospital readmission rates (14.0% vs 16.5%, p=0.82). Disease recurrence within five years occurred in 16.0% of dMMR patients compared with 20.2% of pMMR patients (p=0.63). Conclusion Mismatch repair deficiency was not associated with increased postoperative morbidity following curative colon cancer surgery. Although recurrence rates numerically lower in dMMR tumours, this did not reach statistical significance. These findings support biological distinction of dMMR colon cancer providing reassurance regarding short-term surgical outcomes in this subgroup.