Long-term palliation in metastatic carcinoid tumours with various applications of meta-iodobenzylguanidin (MIBC): pharmacological MIBG, I-131-labelled MIBG and the combination

Carcinoid tumours are rare, but well known for their characteristic present ation with diarrhoea and flushes due to overproduction of serotonin in the case of liver metastases, Treatment is mainly based on the reduction of vas oactive peptide hypersecretion and symptomatic improvement. Octreotide and interferon are widely applied and effective treatment options to induce sym ptomatic improvement and, to a lesser extent, biochemical response. The mai n drawbacks, however, are the need for frequent injections and/or the occur rence of side effects. A rather new approach is the application of metaiodobenzylguanidine (MIBG), which resembles noradrenalin and serotonin, In carcinoid patients, MIBG is taken up in the tumour cells and stored in the neurosecretory granules. Wh en labelled with (131)iodine, radionuclide imaging is positive in up to 70% of the patients. In these patients, two cycles of a therapeutic dose of ra dioactive MIBG may induce long-lasting palliation (8 months) by internal ir radiation, Also, the non-radioactive MIBG compound may be effective in pall iation, even in patients with a negative scan. The mode of action is based on specific tumour acidification as found in animal models, and/or based on its effect as a false neurotransmittor. Three case reports demonstrate different therapeutic possibilities of MIBG: 1) symptomatic relief with unlabelled MIBG, which is a safe and simple tre atment; 2) the longterm palliation following radioactive treatment; and 3) an additional new aspect of predosing with unlabelled MIBG followed by radi oactive MIBG led to improved tumour targeting and impressive clinical respo nse. fur J Gastroenterol Hepatol 11:1157-1164 (C) 1999 Lippincott Williams & Wilkins.