Background: The goal of this study was to delineate the patterns of distant metastasis from colon adenocarcinoma (CAC) and evaluate the survival differences by metastatic patterns.

Methods: Using the Surveillance, Epidemiology, and End Results (SEER) database, we extracted patients diagnosed with stage IV CAC between 2010 and 2016. Kaplan-Meier survival curves were plotted with log-rank tests to compare overall survival (OS) of patients with different metastatic patterns. Univariate and multivariate Cox proportional hazards regression models were used to evaluate the effects of different metastatic patterns on survival outcomes in terms of OS and disease-specific survival (DSS).

Results: A total of 26 170 patients were analyzed. The 3- and 5-year OS were 20.7% and 10.5%, respectively, for patients with stage IV CAC. The most common distant metastatic site was the liver, followed by the lung, bone, and brain, but the frequency differed greatly by histology subtypes. The site of metastasis was a significant prognostic factor for OS and DSS in patients with stage IV CAC, independent of the number of metastatic sites and other clinical and demographic prognostic factors. Using liver-only metastasis as reference, lung-only metastasis was associated with better OS (hazard ratio [HR] = 0.82, 95% confidence interval [CI], 0.71-0.94) and DSS (HR = 0.75, 95% CI, 0.64-0.88). Older age, black race, unmarried status, grade III/IV tumors, advanced tumor-node-metastasis (TNM) stage, proximal colon, elevated preoperative carcinoembryonic antigen (CEA), no surgery of the primary site, and no chemotherapy were independent predictors of poor OS.

Conclusions: The site of distant metastasis and number of metastasis site were independent prognostic factors for survival of patients with stage IV CAC. This study highlights the need for diverse treatment strategies for patients with different metastatic patterns.