Development of a novel prediction model for recurrent stage II colon cancer.

Purpose: Adjuvant chemotherapy is recommended for patients with high-risk stage II colon cancer. High-risk stage II is defined by clinicopathological factors in some guidelines. However, there is no unified definition. The aim of this study was to examine the risk factors and develop a novel model to predict the recurrence of stage II colon cancer.
Methods: Three hundred fifty patients who underwent curative resection for stage II colon cancer at Osaka International Cancer Institute and Yao Municipal Hospital from 2004 to 2012 were included. Clinicopathological factors were assessed in a subgroup of 298 patients (Learning Set), and the relapse-free survival (RFS) rate was evaluated as the main outcome. A statistical analysis was performed using a proportional hazards model to determine the factors associated with RFS and a nomogram was developed to predict recurrence. A second subgroup of 52 independent patients who underwent curative resection in 2012 (Validation Set) was used to validate the nomogram.
Results: The median RFS time was 4.96 years, and recurrence was observed in 35 patients. A univariate analysis revealed that a high serum CEA level, preoperative occlusion, tumor location (left-side colon), lymphatic invasion, and vascular invasion were significantly correlated with RFS. These variables were used to develop the nomogram. The C-index was 0.701 in the learning set and 0.585 in the validation set. Using nomogram points, the patients were classified into low-risk, middle-risk, and high-risk categories.
Conclusion: A recurrence prediction model was developed that integrated multiple risk factors in stage II colon cancer patients. High-risk patients were identified by the nomogram.