More and more evidences suggest that primary colon and rectum tumors should not be considered as a single disease entity. In this manuscript, we evaluate the metastatic patterns of colon and rectum cancers and analyze the potential distribution of metastatic disease in these two malignancies. Data queried for this analysis include colorectal adenocarcinoma (2010-2011) from the Surveillance, Epidemiology, and End Results Program (SEER) database. Metastatic distribution information was provided for liver, lung, bone and brain. All of statistical analyses were performed using the Intercooled Stata 13.0 (Stata Corporation, College Station, TX). All statistical tests were two-sided. Totally, there were 46,027 eligible patients for analysis. We found that colon cancer had a higher incident rate of liver metastasis than rectum cancer (13.8% vs 12.3%), while rectum cancer had a higher incident rate of lung (5.6% vs 3.7%) and bone (1.2% vs 0.8%) metastasis than colon cancer, P<0.001. Colorectal cancer patients with lung metastasis had a higher risk of bone (10.0% vs 4.5%) or brain metastasis (3.1% vs 0.1%) than patients without lung metastases. The 1-year cause-specific survival was not significant different for bone or brain metastasis patients with and without lung metastasis (32.9% vs 38.7%, P=0.3834 for bone, 25.8% vs 36.9%, P=0.6819 for brain). Knowledge of these differences in metastatic patterns may help to better guide pre-treatment evaluation of colorectal cancer patients, especially in making determinations regarding curative-intent interventions.
Keywords: SEER; colon cancer; incidence; metastases; rectal cancer.