Determination of carcinoembryonic antigen levels in peripheral and draining venous blood in patients with colorectal carcinoma Determinação dos níveis do antígeno carcinoembriônico no sangue periférico e no efluente venoso em doentes com carcinoma colorretal

BACKGROUND: The problem of the relationship between blood carcinoembryonic antigen (CEA) levels and tissue CEA content in colorectal carcinoma, and the mechanisms for CEA release from tumor cells in tissue adjacent to the neoplasm is important to understanding the biology of colorectal carcinoma. It has not been adequately explained whether CEA in the peripheral blood is drained mainly by portal system blood or by the lymphatic system, or indeed by both systems. AIM: To study the behavior of CEA levels in peripheral blood (CEA-p) and venous effluent blood (CEA-d) among patients with colorectal tumors, who underwent curative operation. METHOD: A total of 28 patients were studied (12 male [42.9%] and 16 female [57.1%], mean age 66.1 years [range: 43 - 84]). Immediately after laparotomy, peripheral venous blood was extracted by antecubital venous puncture and venous effluent blood was collected from the main drainage vein of the lesions. Values of CEA-p, CEA-d and the gradient between CEA-d and CEA-p that were less than 5.0 ng/mL were considered normal. RESULTS: Eight (28.6%) patients were stage A in Duke's classification, nine (32.1%) stage B and 11 (39.3%) stage C. The neoplasm was located in the rectum of 14 patients (50.0%), in the transverse colon in five (17.9%), in the sigmoid in four (14.3%), in the cecum and/or ascending colon in three (10.7%), and in the descending colon in two (7.1%). The histopathological examination revealed well-differentiated adenocarcinoma in all the patients. Only one patient (3.6%), Duke's classification stage C, presented neoplasm with venous invasion. The gradient between the CEA-p and CEA-d levels were normal in 25 patients (88.3%) and high in three (10.7%). The mean value for CEA-p was 3.8 ± 4.1 ng/mL (0.1-21.1 ng/mL) and for the drained CEA (CEA-d) it was 4.5 ± 4.3 ng/mL (0.3-20.2 ng/mL), without significant difference between these values. There was a significant difference between the mean value for CEA-p and CEA-d levels greater than 5 ng/mL. CONCLUSION: The CEA-p and CEA-d levels in the colorectal carcinoma patients were not shown to be different. The results from this study suggest that, in colorectal neoplasm without venous invasion, there may not be notable CEA drainage from the tumor by the portal vein effluent blood.RACIONAL: O problema da relação entre os níveis de CEA no sangue e o conteúdo de CEA tissular no carcinoma colorretal e os mecanismos de liberação do CEA das células neoplásicas nos tecidos vizinhos