Prognostic Value of a Seven-Factor Risk Stratification System in T3N0 Colon Cancer: A Single-Center Retrospective Study

Background and Objectives: This study aimed to validate the prognostic value of clinicopathologic risk factors and assess the discriminatory performance of a guideline-based seven-factor risk stratification system in T3N0 colon cancer. Secondary objectives included examining the independent prognostic role of mucinous histology and analyzing current adjuvant chemotherapy decision-making patterns. Materials and Methods: A total of 174 patients who underwent curative resection between 2015 and 2025 and were diagnosed with pathologic T3N0M0 (stage IIA) colon adenocarcinoma were retrospectively reviewed. Patients with T4 disease, rectal tumors, synchronous malignancies, neoadjuvant therapy and mismatch repair deficiency (dMMR/MSI-H) were excluded. Seven high-risk factors were defined: lymphovascular invasion (LVI), perineural invasion (PNI), intestinal obstruction, perforation, inadequate lymph node sampling (<12 lymph nodes), poor differentiation (Grade 3 and 4), and high-grade tumor budding (BD3, ≥10 buds according to ITBCC criteria). Mucinous histology was evaluated as a separate subgroup analysis. The primary endpoint was recurrence-free survival (RFS); secondary endpoints were disease-free survival (DFS) and overall survival (OS). Competing risks analysis was performed using the Aalen–Johansen estimator, with death without recurrence as the competing event.