[Tumor markers--personal experience. The use of tumor markers for cancer of digestive organs].

This review is concerned mainly with our experience in the use of tumor markers for cancer of digestive organs from study of tumor markers by the author over the past 20 years. Development of a radioimmunoassay for highly sensitive detection of alpha-fetoprotein (AFP) by Ishii et al. in 1971 enhanced the usefulness of screening for early hepatocellular carcinoma (HCC) occurring in the course of liver cirrhosis. PIVKA-II, reported as a highly specific tumor marker for HCC, was thought to be less available for detection of early HCC occurring in the course of liver cirrhosis in comparison with AFP. Carcinoembryonic antigen (CEA), a most popular and useful tumor marker for cancer of digestive organs, was frequently positive in sera of colorectal cancer patients who had no subjective complaint or physical sign. This experience supported employment of CEA as a routine screening test for colorectal cancer. A survey of routine examinations of serum CA 19-9 for a period of one month in the clinical laboratory of our hospital proved that 92% of the positive cases of low-level CA 19-9 from 37 U/ml to 75 U/ml were noncancerous. This result indicated that the cut-off value of 37 U/ml employed for serum CA 19-9, which had been evaluated as a specific and highly sensitive tumor marker for pancreatic cancer and bile duct cancer, was too low. Accordingly, it was thought necessary to investigate a change of cut off value and reevaluate CA 19-9 for pancreatic cancer and bile duct cancer in comparison with other tumor markers of carbohydrate antigen such as CA 50, sialyl SSEA-1. From our experience in the use of tumor markers, the combination assays of fetal protein such as AFP, CEA, basic fetoprotein (BFP) and carbohydrate antigen, such as CA 19-9 and CA 50, for routine examination of tumor marker, are recommended for effective screening of cancer of digestive organs.