Prognostic values of initial responses to low-dose (131)I-MIBG therapy in patients with malignant pheochromocytoma and paraganglioma

PURPOSE: We retrospectively examined whether or not initial responses of first low-dose (131)I-meta-iodo-benzyl-guanidine radiotherapy ((131)I-MIBG therapy) in patients with malignant pheochromocytoma and paraganglioma had prognostic values. MATERIALS AND METHODS: This study included 26 patients with malignant pheochromocytoma (n = 18) and paraganglioma (n = 8) who underwent the first (131)I-MIBG therapy between October 2001 and September 2007. Based on the initial subjective, hormonal, scintigraphic, and objective responses to (131)I-MIBG therapy, the responses were divided into progression disease (PD) and non-PD. We examined the following factors for prognostic significance: sex, age, disease, initial diagnosis (benign or malignant pheochromocytoma), hypertension, diabetes mellitus, palpitations, symptoms related to bone metastases, and number of low-dose (131)I-MIBG therapy. Univariate Cox proportional regression analysis was used to identify prognostic factors for overall survival. Overall survival was analyzed by Kaplan–Meier method and the curves were compared using the log-rank test. RESULTS: The median survival time was 56 months. In the follow-up period, 16 patients died from exacerbation of their diseases. Univariate analysis showed that the hormonal PD [hazard ratio (HR) 3.20, P = 0.034, confidence interval (CI) 1.09–9.93], objective PD (HR 11.89, P = 0.0068, CI 2.14–65.85), single-time (131)I-MIBG therapy (HR 3.22, P = 0.020, CI 1.21–8.79), hypertension (HR 2.93, P = 0.044, CI 1.02–10.50), and symptoms related to bone metastases (HR 3.54, P = 0.023, CI 1.18–13.04) were bad prognostic factors for overall survival. Kaplan–Meier analysis demonstrated that the hormonal non-PD (P = 0.026), objective non-PD (P = 0.0002), multiple-time (131)I-MIBG therapy (P = 0.013), and no symptom related to bone metastases (P = 0.024) were significantly associated with good prognosis. Overall survival rate was 70 and 50 % at 5 years from the initial diagnosis and from the first (131)I-MIBG therapy, respectively. CONCLUSION: The hormonal and objective responses to the first low-dose (131)I-MIBG therapy as well as complication of hypertension and symptoms related to bone metastases may be prognostic factors in patients with malignant pheochromocytoma and paraganglioma.