Malignant pheochromocytomas and paragangliomas – The importance of a multidisciplinary approach

Abstract 

Approximately 10% of the pheochromocytomas and 20% of the paragangliomas are malignant with poor survival. As the biological behaviour of these tumours cannot be predicted with certainty from pathology the diagnosis of malignancy is difficult. Genetic testing is gaining impact as mutations in the tumour suppressor gene Von Hippel-Lindau and the mitochondrial succinate dehydrogenase enzyme complex subunit B (SDHB) are associated with malignancy. Excess release of catecholamines is characteristic for pheochromocytomas. High levels of chromogranin A, that is co-stored and co-secreted with catecholamines, may indicate tumour mass and malignancy and can be used to monitor response and relapse. The secretory and non-secretory tumours can be visualised with functional (specific and non-specific) imaging as SPECT and PET using ¹²³I-MIBG, somatostatin analogues, ¹⁸F-DOPA, and ¹⁸F-FDG. These modalities are recommended in patients with extra-adrenal and suspected metastatic/malignant disease, in case of distorted post-operative anatomy, and when suspected recurrence. The sensitivities of ¹²³I-MIBG scintigraphy or ¹⁸F-DOPA PET are relatively low in SDHB mutated tumours, but high using ¹⁸F-FDG. Specific PET imaging with somatostatin analogues generally has high sensitivity in malignant disease. There are no curative therapeutic options for malignant, metastatic pheochromocytomas/paragangliomas, wherefore consolidation of quality of life is essential. Adjuvant radionuclide treatment with beta-emitting isotopes coupled to MIBG or somatostatin analogues have shown response in approximately 30%. Chemotherapy is restricted to patients not accessible for surgery and resistant to radionuclide therapy. Novel targeted therapies, which mainly through a cytostatic effect interfere with specific targeted molecules needed for carcinogenesis and tumour growth show encouraging results.

Keywords: Pheochromocytoma, Paraganglioma, Adrenal mass, Multi-modality imaging, MIBG, SSTR, PRRT