Comparison of carcinoembryonic antigen levels between portal and peripheral blood in patients with colorectal cancer. Correlation with histopathologic variables.

Correlation between carcinoembryonic antigen (CEA) levels of peripheral and portal blood, and eight histopathologic variables, was examined in 66 patients with colorectal cancer. The change in CEA levels in the portal blood of 40 patients during operation was also examined in relation to histopathologic variables. CEA levels of portal blood (with a mean of 26.6 ng/ml and positive rate greater than 5 ng/ml, 59.1%) were significantly higher than those of peripheral blood (8.1 ng/ml, 33.3%). Elevation of CEA levels in portal and peripheral blood was most highly correlated with the venous invasion. Although the levels in the portal blood were related to six other histopathologic variables including tumor size, tumor differentiation, node metastasis, lymphatic invasion, invasive layer of the colorectal wall, and Dukes' classification except tumor location. CEA levels rose from 19.4 ng/ml and 40% to 43.6 ng/ml and 90.2% respectively following operative stimuli to cancer lesions with venous invasion. However, the levels did not rise in the lesions without the invasion. CEA levels of peripheral blood were as low as 5 ng/ml in three out of eight patients with liver metastasis. However, the levels in portal blood were much greater than 5 ng/ml in all of the patients. These results suggest that CEA may be hematogenously drained by the portal system via the draining vein from the cancer cells in the invasive veins but not by the thoracic duct of the lymphatic system.