ALPHA-SUBUNIT AND HUMAN CHORIONIC GONADOTROPIN-BETA IMMUNOREACTIVITY IN PATIENTS WITH MALIGNANT ENDOCRINE GASTROENTEROPANCREATIC TUMORS

In the serum of patients with malignant endocrine gastroenteropancreat ic (GEP) tumours, both alpha-subunit (alpha-SU), common to all glycopr otein hormones, as well as free beta-subunit of human chorionic gonado tropin (hCG-beta) have been reported to be elevated in a substantial f raction. Both have been discussed as markers of malignancy in these ne oplasms. In the present study we evaluated the diagnostic significance of alpha-SU and hCG-beta as serum markers in patients with malignant endocrine gastroenteropancreatic tumours. The study group consisted of 52 patients with endocrine GEP-malignancies (24 nonfunctioning, 23 ca rcinoid syndromes, four gastrinoma, one glucagonoma), located in the s mall intestine (n = 29), pancreas (n = 17), colon or rectum (n = 3), r etroperitoneum (n = 2) and stomach (n = 1). alpha-SU and hCG-beta immu noreactivity was also assessed in the serum of patients with benign GE P-tumors (five insulinoma, and three gastrinoma). Concentrations of al pha-SU and hCG-beta were determined using two highly sensitive and spe cific immunoradiometric assays employing two monoclonal antibodies eac h. In 19 of 52 patients (37%), either alpha-SU (n = 9), hCG-beta (n = 7) or both subunits (n = 3) were elevated. In the subgroup of 24 patie nts with nonfunctioning GEP-tumours, increased concentrations of eithe r alpha-SU (n = 6) or hCG-beta(n = 3) or both subunits (n = 1) were fo und in 10 of 24 patients (42%). In four of 23 patients with carcinoid syndrome (17%), either alpha-SU (n = 2), hCG-beta(n = 1) or both subun its (n = 1) were above the normal range. Of five patients with functio nally active endocrine pancreatic islet cell tumours, all had an eleva tion of at least one of the two substances. In contrast, in the serum of all eight patients with benign GEP-tumours, alpha-SU and hCG-beta w ere within normal limits. In summary, our data show a high frequency o f elevated alpha-SU or hCG-beta immunoreactivity in the serum of patie nts with malignant endocrine gastroenteropancreatic tumours. Since imm unoreactivity is mostly discordantly elevated, the two markers are wel l suited to supplement each other. Absolute values had a similar range in the subgroups analysed. The prevalence was highest for functionall y active endocrine pancreatic islet cell cancers, but nonfunctioning e ndocrine GEP-malignancies also exhibited a high frequency of predomina ntly alpha-SU immunoreactivity. This is important since this subgroup of endocrine GEP-tumours usually lacks hormonal markers. In patients w ith carcinoid syndrome, however, increased serum levels of alpha-SU or hCG-beta appear to be rare and of no diagnostic value.