Repeated [131I]metaiodobenzylguanidine therapy in two patients with malignant pheochromocytoma.

Context: Approximately 10% of pheochromocytomas are malignant with a 5-yr survival rate of less than 40%. Promising results have been published on single high-dosage [131I]metaiodobenzylguanidine ([131I]MIBG) treatment for malignant pheochromocytoma. We present our experience with multiple intermediate-dosage [131I]MIBG therapy instead of single high-dosage therapy.
Setting and Patients: The study took place at University Medical Centers and included two patients (one male, 36 yr of age, and one female, 43 yr of age) with widely spread metastatic pheochromocytoma and bad prognosis because of liver and lung metastases.
Interventions: Instead of a single high dosage, these two patients were treated with multiple intermediate dosages of [131I]MIBG. The first patient received 37 GBq (1 Ci) [131I]MIBG in five sessions [7400 MBq (200 mCi) each; interval range, 2-11 months]; the second patient received 66.6 GBq (1.8 Ci) [131I]MIBG in 12 sessions [5550 MBq (150 mCi) each; interval range, 2-14 months].
Outcome Measures: We measured efficacy, toxicity, and survival.
Results: Both patients had a complete symptomatic response and a partial tumor volume response. The first patient had a partial biochemical response, the second a complete biochemical response. In both cases, toxicity has been confined to nausea during treatment. Hematological toxicity was minimal, and both patients stayed euthyroid. The survival (so far) of these patients was 5 yr (clinical case 1) and 16 yr (clinical case 2) after initial diagnosis.
Conclusions: Repeated intermediate-dosage [131I]MIBG treatment appears to be a reliable and well-tolerated radionuclide therapy and might be a useful adjunct in patients with malignant pheochromocytoma, providing longstanding palliation and prolonged survival.