Gastrointestinal Neuroendocrine Tumors: Pancreatic Endocrine Tumors

Abstract

Pancreatic endocrine tumors (PETs) have long fascinated clinicians and investigators despite their relative rarity. Their clinical presentation varies depending upon whether the tumor is functional or not and also according to the specific hormonal syndrome produced. Tumors may be sporadic or inherited but little is known about their molecular pathology, especially the sporadic forms. Chromogranin A appears to be the most useful serum marker for diagnosis, staging and monitoring. Initially, therapy should be directed at the hormonal syndrome as this has the major initial impact on the patient's health. Most PETs are relatively indolent but ultimately malignant, except for insulinomas which are predominantly benign. Surgery is the only modality that offers the possibility of cure although it is generally noncurative in patients with Zollinger-Ellison syndrome or nonfunctional PETs with MEN1. Preoperative staging of disease extent is necessary to determine the likelihood of complete resection though debulking surgery is often felt to be useful in unresectable patients. Once metastatic, biotherapy is usually the first modality employed because it is generally well tolerated. Systemic or regional therapies are generally reserved until symptoms occur or tumor growth is rapid. Recently a number of newer agents, as well as receptor-directed radiotherapy, are being evalulated for patients with advanced disease. This review addresses a number of recent advances regarding the molecular pathology, diagnosis, localization and management of PETs including discussion of peptide receptor radionuclide therapy and other novel antitumor approaches. We conclude with a discussion of future directions and unsettled problems in the field.