Sinnvoller Einsatz von Tumormarkern

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.