Stieber, Petra; Heinemann, Volker
Sinnvoller Einsatz von Tumormarkern.
In: Laboratoriumsmedizin - Journal of Laboratory Medicine, Vol. 32, Nr. 5: S. 339-360
Tumor markers refer to all detectable and measurable analytes which are able to indicate a solid tumor or contribute to its characterization or judgment concerning tumor spread and therapy efficacy. Among the markers, humoral circulating tumor substances, such as precursors of normal antigens, ectopically produced hormones or enzymes, ontogenetic old reactivated antigens, hybridoma-defined mucins and cytokeratins are of special interest. Up to now, no tumor specific biomarker has been detected, all markers known so far are physiological components of blood; thus, their diagnostic capacity is more related to quantity than to quality. The tumor marker concentration depends on the tumor blood supply and reflects tumor mass and tumor spread as a sum of marker expression, synthesis, release, the catabolism of the organism, as well as the marker excretion. Changes in biomarker levels without correlation to tumor load can be due to impairment of the liver and kidney function or due to invasive diagnostic methods (endoscopy, biopsy, ureteral catheter) or due to acute reactions on treatment (surgery, radio-chemotherapy). Due to problems with standardization between assays from different producers measuring the same antigen, interpretation of biomarkers of single measurements, such as PSA (prostate specific antigen), must be performed using assay specific reference ranges and interpretation of serial measurements must be performed using the identical assay. The test result has to be indicated together with the assay used (kit and producer). Among the potential indications for tumor marker determinations, the early detection or screening of a tumor is unrealistic - except PSA in prostate cancer detection. In rare cases, biomarkers can be helpful in tumor localization (HTG (human thyreoglobuline), PSA) and support of primary diagnosis, the knowledge about their prognostic relevance is increasing, the most widely used indication is therapy control and follow-up care in context with medical imaging. Provided that markers are critically selected following the localization of the tumor, that serial determinations are performed using the identical assay and that the clinical question is relevant, tumor markers contribute to a significant degree to diagnosis, prognosis, therapy control and early detection of metastatic or recurrent disease. Especially in the field of diagnostic oncology, the quality of the investigator is significantly linked to the quality of the test result.