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.