[Sensitivity and specificity of tumor markers in cancer diagnosis]

Each serum tumor marker has its own sensitivity and specificity. The sensitivity is the true positive rate in malignant cases, and the specificity is the true negative rate in benign cases. We should ascertain various benign diseases or triggers which tend to show false-positivity, especially in the measuring of CA19-9, CA125, and acute phase reactants, such as, IAP and TPA. Cancer-specificity is high in sialyl-stage-specific embryonic antigen-I, sialyl-Tn antigen, and NCC-ST-439, etc. Organ-specificity is considerably high in the case of some markers, such as, alpha-fetoprotein, elastase-I, and neuron-specific enolase, etc. On the other hand, the organ-specificity of carcinoembryonic antigen is low. Therefore, the combination of different categories of tumor markers is of great importance. Recently, molecular diagnosis of cancer is being developed. However, even K-ras oncogene mutations at codon 12 are not absolutely specific to pancreatic cancer from genetic analysis of pancreatic juice endoscopically aspirated from patients with pancreatic diseases. Improvement of sensitivity and specificity is still one of the most important issues in the research and development of tumor markers.