[Status quo of tumor markers and important points in medical practice]

Tumor markers is a term describing substances produced by tumor cells or in response to tumor cells, and new tumor markers have been found with the progress of examination modalities. Not only Bence-Jones protein and M protein by immunoelectrophoresis, and AFP and CEA by immunochemical analysis, but also hormones, enzymes, and embryonal cancer related substances have been employed for a long time. Recently, a variety of new tumor marker tests have been developed, such as those using monoclonal antibodies that recognize carbohydrate antigens, bone metabolism markers to evaluate bone metastasis of cancer by the type I collagen metabolites, and gene markers to examine oncogenes and tumor suppressor genes by gene cloning and the PCR method. Early detection and diagnosis are keys to countermeasures against cancer, and tumor markers are regarded as a powerful tool for early detection of cancer. However, any tumor marker can be positive without cancer. In addition, problems arise because tumor markers often show negative for early cancer or even advanced cancer. As a result, no ideal tumor marker has been found. Tests of tumor markers aim to screen high-risk patients, differentiate tumor types, monitor therapeutic efficacy, and detect recurrences early. It is important to raise the diagnostic efficiency by avoiding the selection of similar markers in antigenicity, and instead combining two to three markers with little association.