[Comparison between the gastrointestinal tumor antigen and the carcinoembryonic antigen in diseases of the digestive tract].

Recently a glycolipid antigen known as gastrointestinal cancer antigen (GICA) has been proposed as a new seral marker of gastrointestinal and pancreatic tumours. This antigen is specifically recognised by a monoclonal antibody and biologically and immunologically distinguished by carcinoembryonic antigen (CEA). Out of 438 subjects including: 60 blood donors, 205 patients suffering from digestive tract tumours, subdivided into different organs 21 gastric ca's, 60 colon ca's, 100 pancreatic ca's and 24 liver cancers) 173 subjects with inflammatory gastrointestinal complaints, also divided by organ 18 gastric ulcers, 45 inflamed colons, 60 chronic pancreatitis and 50 liver cirrhosis). GICA and CEA radioimmunoassays were carried out (Sorin GICAK and CEAK) to evaluate sensitivity, specificity and predictive accuracy. Normal threshold levels were set at 30 ng/ml for CEA and 40 mu/ml for GICA. These levels represent the mean + 2DS of levels measured in 260 patients hospitalised for various benign and functional complaints and differ from cancer patient results by the largest amount. All blood donors, whether smokers or not, give lower values than these. Results show GICA gives a lower overall number of false positives than CEA (20% as against 9.6%). GICA diagnostic results were more accurate overall for the entire case sample examined. GICA gave higher percentage positives than CEA for individual tumour types: pancreatic ca (82% v 52%), liver cancer (70.8% v 20.8%) and gastric ca (47.6% v 33%). CEA appears to work better than GICA in the case of colorectal ca's (56% v 41%). Both markers were found to be more sensitive in the presence of tumours with metastases. GICA is the best currently available marker of pancreatic tumours thanks to its sensitivity, specificity and predictive accuracy. Although GICA gave good results in cases of liver cancer, these did not exceed those obtained with alpha foetoprotein. In the other cases of digestive tumours examined, a combination of GICA and CEA investigation techniques appears to be the best non-invasive method currently available for patient follow-up.