Stage IV colorectal cancer primary site and patterns of distant metastasis

Background: Although colorectal cancer (CRC) usually metastasizes to the liver and/or lungs, factors influencing the anatomic pattern of metastases remain poorly understood. Methods: We assessed the relationship between primary CRC site and pattern of synchronous metastasis among 1202 individuals diagnosed with incident metastatic CRC between 2010 and 2014 and identified through the Seattle-Puget Sound Surveillance, Epidemiology, and End Results (SEER) registry. Polytomous logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association between primary tumor site and synchronous metastatic pattern. Results: Compared to patients with proximal colon primaries, patients with rectal primaries were more likely to present with lungs-only or liver and lungs metastases versus liver-only metastases (ORlungs-onlyvs.liver-only: 2.39, 95% CI: 1.35-4.24, ORliver+lungsvs.liver-only: 2.20, 95% CI: 1.46-3.32). Conclusion: These findings suggest that patients with rectal primaries are more likely than patients with colon primaries to present with synchronous lung metastases. (C) 2017 Elsevier Ltd. All rights reserved.