TNMD system- A better staging in predicting prognosis of patients with stage III colon cancer

Purpose: Our study aimed to emphasize the effect of tumor deposit (TD) on the prognosis of stage III colon cancer patients and suggested the possibility of staging adjustment. Methods A total of 14148 patients with stage III colon cancer were enrolled from the Surveillance, Epidemiology, and End Results (SEER) database. Cox regression analysis was used to evaluate the effect of TD on prognosis. Our study concentrated on the clinicopathological characteristic of patients with TD positive. 956 patients from the Harbin Medical University Cancer Hospital were enrolled as external validation cohort. Results Multivariate analysis determined that TD was an independent prognostic risk factor. Patients with regional lymph nodes (RLN) (+), TD (+) were associated with more perineural invasion (13.1% vs. 27.4%), T4 (17.9% vs. 30.0%), poorly differentiated (21.9% vs. 26.4%) and N2 (30.2% vs. 42.7%). Therefore, our study combined the status of TD and four risk factors to construct the tumor-node-metastasis-deposits (TNMD) staging system. In the new staging system, patients with RLN (+), TD (+) were divided into stage IIID (0–1) and stage IIIE (2–4) according to the number of risk factors. The estimated 5- year overall survival (OS) rates were significantly different between IIID and IIIE (61.9% vs 42.1%). In conclusion, the TNMD staging system was a reliable predictor for the OS of patients with stage III colon cancer. Conclusion Compared with the TNM system, the TNMD staging could better reflect the effect of TD on patients with stage III colon cancer and provide a more precise prognosis.