gms | German Medical Science

Aim: Intravenous iodine-131 meta-iodobenzylguanidine [I-131-MIBG] has been used for systemic targeted radiotherapy of advanced neuroendocrine tumors [NET] including metastatic carcinoid tumors [Carc] in smaller studies. Different therapeutic activities have been applied usually ranging between 100 and 300 mCi per course. The purpose of this study was to evaluate the treatment response and outcome for the group of advanced Carc as well as toxicity data including other NET for a fixed therapeutic regime using 300 mCi I-131-MIBG per course.

Methods: We performed a retrospective review of 27 patients with advanced metastatic NET (Carc: n=16; other: n=11) treated at our institution. While treatment response and outcome was analyzed for the major patient group (Carc), toxicity of therapy was reviewed for all 27 patients. I-131-MIBG therapy was performed with 300 mCi per course and minimum intervals of three months. Radiological response was assessed by CT and/or MRI on regular follow-up examinations. Toxicity was evaluated by extensive laboratory tests including complete blood counts, hepatic and renal function tests.

Results: Radiological response in the group of Carc: minor response [MR] in 12.5%, stable disease [SD] in 75% with mean TTP=46 months (95% CI: 30-62), progressive disease [PD] in 12.5% of patients. Nine patients with functioning Carc were evaluable for symptomatic response showing complete response [CR] in 33%, PR in 44%, and SD in 22%. Mean overall survival in Carc was 52 months (95%CI: 38-66) and mean progression-free survival 42 months (95%CI: 27-57). Toxicity referring to the total number of applied treatment courses (n=66) was as follows: reversible bone marrow toxicity (CTC grade 3-4) with leucopenia in 12% and thrombopenia in 2%, temporary nausea in 27% and vomiting in 8% of applied therapy cycles. No hepatic or renal toxicities were noted.

Conclusions: The presented I-131-MIBG treatment of advanced carcinoid tumors is well tolerated, offers effective symptom palliation and generally achieves disease stabilization for an average of 4 years. However, patients seem to particularly benefit in terms of prolonged survival with a mean of 52 months, which compares favorably to an epidemiologic survival of 24-42 months [Ref. 1]. This form of targeted radiotherapy thus, deserves serious consideration as a treatment alternative for non-resectable metastatic carcinoid tumors and should be evaluated by multi-center studies.