[Limitation of clinical usefulness of tumor marker]

The clinical features and limitations of the usefulness of 10 kinds of main tumor markers such as AFP, CEA, CA 19-9 etc. are described in detail in this paper. This review is concerned with the limitation of the clinical usefulness of tumor marker. Evaluation of tumor marker is directed toward usefulness for diagnosis and the monitoring of cancer. The main weak points in the diagnosis of cancer by tumor marker have been insufficient sensitivity for detection of cancer and specificity to cancer. The sensitivity for detection of early cancer by tumor marker is especially low, and many tumor markers have ordinarily high false positive incidence for benign liver disease. On the other hand, limitation of specificity to organ is found in most tumor markers. Most tumor markers generally considered to be organ-specific are in fact, non-organ-specific, such as CA 19-9, which is thought to be specific to pancreatic cancer. On the other hand, there are few strictly organ-specific tumor markers such as prostate-specific antigen (PSA) and PIVKA-II. The usefulness of tumor marker for monitoring cancer is considered far better than that for diagnosis of cancer. However, a tumor marker in cases with less than the cut-off value is not available for monitoring of cancer.