Prognostic values of initial responses to low-dose 131I-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.