The impact of microsatellite instability and tumor characteristics on survival of patients with right-sided colon cancer.

[AIM] This study aimed to explore the clinical and pathological differences between microsatellite instability-high (MSI-H) and microsatellite stable (MSS) tumors in right-sided colon cancer patients, as well as to evaluate the prognostic significance of MSI status on survival outcomes.

[METHODS] Historical records of patients who underwent surgery for right-sided colon cancer between 2016 and 2024 were evaluated retrospectively. Immunohistochemistry was used for the determination of MSI status, and data on tumor characteristics, lymph node metastasis, carcinoembryonic antigen (CEA) levels, and survival outcomes were analyzed. Comparisons were performed to assess differences between the MSI-H and MSS groups, where P < .05 was considered statistically significant.

[RESULTS] The study included 100 patients, consisting of 52 men and 48 women with a median age of 72 (range: 63-79). Tumors with MSI-H status were significantly larger (median: 6.50 cm vs 4.50 cm; P < .001) and demonstrated higher rates of mucinous carcinoma (52.9% vs 24.2%; P = .008) compared to MSS tumors. Poor differentiation was more common in MSI-H tumors (20.6% vs 3.03%: P = .003). Overall survival (OS) and disease-free survival (DFS) did not differ significantly between MSI-H and MSS groups (P = .466 and P = .337, respectively). Elevated postoperative CEA levels at 6, 12, 18 and 24 months were significantly associated with poorer survival outcomes (P < .01).

[CONCLUSION] Right-sided colon cancers with MSI-H status were associated with larger tumor size, mucinous histology, and poor differentiation but did not significantly affect survival outcomes. Postoperative CEA monitoring provides critical prognostic information. Further large-scale studies are required to confirm these findings and refine therapeutic approaches.