High-dose MIBG therapy stabilizes neuroendocrine tumors

Dose-intensification of systemic cancer therapy with I-131 metaiodobenzylguanidine (I-131 MIBG) may be ideal for palliative treatment of neuroendocrine tumors, according to a study published Oct. 7 in the Journal of Nuclear Medicine.

Previous dose protocols have ranged from 100 and 300 mCi, but some institutions are administering 600 or more mCi with potential stem cell therapy. Researchers including Samer Ezziddin, MD, from the department of nuclear medicine, University Hospital in Bonn, Germany, retrospectively reviewed the cases of 31 neuroendocrine cancer patients who received the institution’s protocol of 300 mCi of the radiolabeled somatostatin analog to evaluate toxicity and therapy response with a relatively high treatment dose.

Other studies have shown that systemic I-131 MIBG is an effective treatment for carcinoid tumors as well as paraganglioma, neuroblastoma and pheochromocytoma. The patient cohort for this study included 20 patients with carcinoid tumors and 11 with other varieties of neuroendocrine cancer. Results of the research showed that 80-90 percent of patients achieved stabilization of disease, with 80 percent in a median of 34 months. Of 11 symptomatic patients with functioning carcinoid tumors, three achieved complete resolution of symptoms and six additional patients experienced some level of improvement with minimal adverse effects.

“The favorable survival and limited toxicity suggest that high cycle activities are suitable and that this modality may be used for targeted carcinoid treatment—either as an alternative or as an adjunct to other existing therapeutic options,” wrote Ezziddin et al.

Range of treatments for the retrospective study included cases of at least two courses of I-131 MIBG therapy at intervals of three months. Repeat cycles were contingent on response to therapy and the wishes of individual patients. Further dose-intensification for difficult-to-treat cases of neuroendocrine cancer, such as those involving carcinoid tumors, may be desirable to improve health outcomes for these patients.