Tumour size and overall survival among surgically treated patients with non-metastatic colon cancer in the U.S. Military Health System

Aim: Larger tumour size and lymph node involvement traditionally predict poorer survival in colon cancer patients. However, it has been recently suggested that very small tumours (<5 mm) may be a predictor of poor prognosis in colon cancer patients when lymph nodes are involved. This study investigated whether node-positive colon cancer patients with small tumours had worse survival compared to those with larger tumours in the Department of Defense’s (DoD) Military Health System (MHS), a universal health care system. Methods: Surgically treated colon cancer patients were identified from the DoD's Automated Central Tumour Registry (ACTUR). These patients were diagnosed with Stage I–III colon cancer between 1989 and 2010, had one or more lymph nodes examined, did not receive pre-operative radiotherapy and were followed through 2013 to determine vital status. Multivariable Cox models were used to examine survival differences according to tumour size, and data were stratified by lymph node status and age. Results: There were no differences in overall survival according to tumour size in the study population. These findings remained similar in analyses stratified by lymph node status and age. Conclusion: In a universal healthcare system, small tumour size is not associated with worse prognosis in node-positive colon cancer patients.