sincalide and Carcinoma--Medullary

Cholecystokinin (CCK)-B receptors have been demonstrated on a high percentage of medullary thyroid carcinomas (MTC) in vitro. After encouraging results both in vitro and in animal studies, we studied the efficacy of an octapeptide [111In-DTPA]-CCK analogue in seven patients with MTC. In four of five patients in whom serum calcitonin levels were monitored, a significant rise was found following the injection, indicating retained biological activity of the radiopeptide. In all patients there was visualization of the CCK-B receptor-positive stomach. In one of two patients with known MTC lesions, some of the lesions were visualized; in addition some lesions were visualized in one of the five other patients who had elevated serum tumour markers but negative localizing studies. Radioactivity in the presumed tumour sites was still present at 48 h p.i. The uptake in the presumed tumour sites and stomach was low. Background radioactivity dropped rapidly owing to urinary excretion. After 1 h, breakdown products of the labelled analogue predominated both in urine and in serum, and virtually no intact peptide was present.. (1) the CCK-B receptor-positive gastric mucosa and presumed MTC lesions could be visualized in patients using an octapeptide [111In-DTPA]-CCK analogue that is probably internalized, proving the feasibility of CCK-B receptor imaging in vivo; (2) there was a relatively low uptake of the CCK analogue in the strongly CCK receptor positive stomach, and rapid degradation of the peptide in serum.

Topics: Carcinoma, Medullary; Humans; Indium Radioisotopes; Pentetic Acid; Radionuclide Imaging; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sincalide; Thyroid Neoplasms; Tissue Distribution

The 2 gastrointestinal peptides cholecystokinin (CCK) and gastrin, which act through CCK-A receptors (having high affinity for CCK) or CCK-B/gastrin receptors (having high affinity for CCK and gastrin), are considered to be important tumor growth factors. We have evaluated CCK-A and CCK-B/gastrin receptors in 34 human thyroid cancers using in vitro receptor autoradiography with 2 different radioligands. We demonstrate high-affinity CCK-B/gastrin receptors in medullary thyroid carcinomas, present at very high incidence (92%) but the absence of these receptors in non-medullary thyroid carcinomas or in normal thyroid glands. CCK-B/gastrin receptors are therefore likely to be the molecular substrate for the pentagastrin-stimulation test, widely used in medullary thyroid carcinomas; moreover, they represent the targets for physiologically secreted gastrin or CCK which, as growth factors, may stimulate the growth of medullary thyroid carcinomas. Furthermore, these results have diagnostic as well as therapeutic implications: radiolabeled gastrin and CCK analogs may be used for scintigraphic tumor localization in vivo, whereas CCK-B-selective antagonists may be of therapeutic value.

Topics: Autoradiography; Carcinoma, Medullary; Cholecystokinin; Gastrins; Humans; Iodine Radioisotopes; Receptor, Cholecystokinin A; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sincalide; Thyroid Neoplasms