Abstract
1193
Objectives High dose131I metaiodobenzylguanidine (MIBG) radiotherapy (12mCi/kg) has shown slightly improved survival in patients with malignant pheochromocytoma (PHEO) and paraganglioma (PGL). At the same time, the high dose MIBG therapy increases toxicity including hematologic and pulmonary toxicity. Thus, alternative therapeutic options are required. The purpose of this study was to investigate the effects and safety of repeated MIBG radiotherapy in patients with metastatic PHEO and PGL.
Methods 8 patients with metastatic PHEO or PGL (age 51±11) were prospectively treated with I-131 MIBG. These patients repeated 150 mCi of MIBG therapy within 6 months intervals. Mean treatments were 2.8 ±0.4 times and mean cumulative MIBG dose was 412.5±65.0 mCi (7.5mCi/kg). The hormonal, tumor responses by computed tomography (CT), and complete blood cell counts were observed before and after the MIBG treatment.
Results 3 patients showed partial remission and 5 patients were stable based on CT findings. Sum longest diameter did not change after MIBG therapy (259.4±258.0 vs 216.1±258.0 mm, ns) Urinary norepinephrine and vanillyl mandelic acid were significantly reduced after the MIBG treatment (938.4±1391.5 to 281.7±151.5 μg/day, P<0.01, 30.4±26.8 to 14.7±17.2 mg/day, P<0.01). WBC (5051±1710 to 4000±1694, P<0.01) and platelet (28.2±9.0X104 to 18.1±6.2 X104, P<0.01) were reduced. However, there was no patient needed to supportive therapy for hematologic toxicity and was no other significant toxicity.
Conclusions Repeated MIBG therapy was able to prevent disease progression and showed hormonal improvement without significant side effects. Therefore, relatively short period of repeated MIBG treatment might be one of the therapeutic options in patients with metastatic pheochromocytoma or paraganglioma