Palliative effect of metaiodobenzylguanidine in metastatic carcinoid tumors

Purpose: To evaluate the therapeutic effect of iodine-131-labeled metaiodobenzylguanidine (I-131-MIBG) and unlabeled MIBG in patients with carcinoid tumor. Materials and Methods: A therapeutic dose of 7.4 GBq (200 mCi) I-131-MIBG infused over 4 hours was administered to 30 patients with either carcinoid syndrome (n = 20) or tumor symptoms such as pain and fever due to carcinoid tumor (n = 10). In general, two courses were given, 6 weeks apart. Due to radioactivity, patients had to be isolated for 5 to 7 days. Subsequently, we studied the effect of unlabeled MIBG based on the possible pharmaceutic activity of MIBG and to avoid the isolation procedure. A dose-escalation study of 8.5, 17, and 34 mg/m(2) MIBG infused over 4 hours at 4-week intervals was performed in 20 patients with carcinoid syndrome who were not suitable for treatment with the radioactive compound. Results: Following I-131-MIBG treatment, symptomatic responses were observed in 60% of patients (median duration, 8 months; maximum, 2 years). Side effects were mild and rapidly reversible in 16 patients, and were related to the isolation procedure in seven of these patients. Unlabeled MIBG resulted in symptomatic improvement in 60% of patients (median duration, 4.5 months). Side effects, which included changes in blood pressure, were mild and transient. Symptomatic responses were not accompanied by biochemical responses. Conclusion: Both MIBG treatment regimens were equally effective in the palliation of symptoms, but duration of response tended to be much longer with the radioactive compound. However, the unlabeled compound provided a simpler treatment, eg, in elderly patients and those in poor condition, without the need for isolation. (C) 1996 by American Society of Clinical Oncology.