BIOCHEMICAL MARKERS IN SERUM AND URINE IN THE WORKUP OF PATIENTS WITH NEUROENDOCRINE TUMORS

Abstract

This review summarizes current data on neuroendocrine tumors (NET), which, unlike other neoplasms, are able to produce biologically active substances (hormones, vasoactive peptides, amines). It is exactly their main characteristic that allows to unify this heterogeneous group and that may determine their clinical course. We present integrated recommendations for biochemical diagnosis and confirmation of over-secretion syndromes based on a  panel assessment of NET biochemical markers. Data from the literature are reviewed on evaluation of clinical significance of generic and specific NET markers, as well as the results of the studies performed by the authors themselves. Three hundred and thirty patients were examined with NETs of various localization (pancreas, stomach, small intestine and large intestine, lungs) and with metastatic NET disease with unknown primary location, who were treated in the N.N. Blokhin Russian Cancer Research Center. The control group included 115 healthy individuals. Before and during the treatment, plasma and serum chromogranin A (CgA) and serotonin levels, as well as 5-hydroxyindoleacetic acid (5-HIAA) in a  24-hour urine sample were measured with standardized immunoenzyme plate-based assays (“Chromogranin A ELISA kit”, Dako A/S; “Serotonin ELISA and 5-HIAA ELISA”, IBL International GMBH). We evaluated clinical importance of CgA as a generic NET marker, as well as that of serotonin and its metabolite 5-HIAA as specific markers of the carcinoid syndrome. CgA was shown to be the most efficient biochemical marker for diagnosis, assessment of prevalence and monitoring of NETs. CgA has a  high diagnostic sensitivity (63.4 to 88.9%) in various NETs. An association between CgA secretion and prevalence and biological activity of the tumor was confirmed. CgA measurement is particularly important in functionally inactive tumors, where serotonin and 5-HIAA have lower sensitivity, being specific markers of the carcinoid syndrome.