Molecular and Therapeutic Advances in the Diagnosis and Management of Malignant Pheochromocytomas and Paragangliomas

Abstract

Abstract Learning Objectives Discuss the advances in molecular genetics which have uncovered new hereditary and germline mutations contributing to the development of pheochromocytoma and paraganglioma and identify the genotype/phenotype patterns which facilitate more accurate determination of malignant potential. Describe the current imaging modalities used in the diagnosis of pheochromocytoma and paraganglioma and evaluate the efficacy of functional imaging modalities according to tumor genotype. Evaluate the current preclinical molecular research contributing to the selection of targeted therapies for malignant pheochromocytoma and paraganglioma. Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare catecholamine-secreting tumors derived from chromaffin cells originating in the neural crest. These tumors represent a significant diagnostic and therapeutic challenge because the diagnosis of malignancy is frequently made in retrospect by the development of metastatic or recurrent disease. Complete surgical resection offers the only potential for cure; however, recurrence can occur even after apparently successful resection of the primary tumor. The prognosis for malignant disease is poor because traditional treatment modalities have been limited. The last decade has witnessed exciting discoveries in the study of PCCs and PGLs; advances in molecular genetics have uncovered hereditary and germline mutations of at least 10 genes that contribute to the development of these tumors, and increasing knowledge of genotype-phenotype interactions has facilitated more accurate determination of malignant potential. Elucidating the molecular mechanisms responsible for malignant transformation in these tumors has opened avenues of investigation into targeted therapeutics that show promising results. There have also been significant advances in functional and radiological imaging and in the surgical approach to adrenalectomy, which remains the mainstay of treatment for PCC. In this review, we discuss the currently available diagnostic and therapeutic options for patients with malignant PCCs and PGLs and detail the molecular rationale and clinical evidence for novel and emerging diagnostic and therapeutic strategies.