Context: Inoperable or metastatic phaeochromocytoma (PC) and paraganglioma (PGL) present a management challenge with high variability in response to systemic therapies. The aim of this study was to assess efficacy and toxicity from two therapeutic radiopharmaceutical agents; Iodine-131 metaiodobenzylguanine (I-131 MIBG) and Lutetium-177-DOTA-octreotate (Lu-177-DOTATATE).
Methodology: This retrospective audit assessed efficacy of radionuclide therapy utilising three variables to assess response; clinical (symptoms and anti-hypertensive medication dose changes), functional (catecholamine levels) and radiological (tumour size).
Results: 16 treatment naïve patients were included in this study: nine patients were diagnosed with PC and seven PGL. Eight patients received I-131 MIBG and eight Lu-177-DOTATATE. There was a significant fall in the mean systolic blood pressure following administration of radionuclide therapy; 133mmHg [IQR 124.5-145.5] to 127mmHg [IQR 112.5-130.8] (p = 0.05). Disease control rate was high for all variables (composite clinical 92%; functional 100%; radiological 100%). Overall response rate was greatest clinically with patients predominantly showing stable disease radiologically (composite clinical 83%; functional 45%; radiological 8%). Median PFS (defined as progression in any clinical, functional or radiological variable) was 17 months with no difference in those receiving I-131 MIBG (16 months, range 5-24 m.) compared with Lu-177-DOTATATE (27 months, range 3-40 m.)(95% CI 0.16-2.3, p = 0.46)
Conclusion: Patients diagnosed with inoperable and metastatic PC/PGLs have few therapeutic options. We have shown utility of I-131 MIBG and Lu-177-DOTATATE in symptomatic management, blood pressure control and hormone secretion, and stabilisation of tumour growth.