Diagnosis and management of insulinoma: current best practice and ongoing developments

Abstract

Insulinoma is a predominantly benign and rare neuroendocrine tumor. Patients with insulinoma typically present with neurologic symptoms from hypoglycemia, such as confusion, dizziness, and behavioral changes, as well as symptoms from a surge in catecholamine levels, such as palpitations, diaphoresis, and tachycardia. Symptomatic patients usually have glucose levels below 55 mg/dL and are relieved of their symptoms when carbohydrate is administered. The 48-hour test, performed by measuring blood glucose levels of insulin, C peptide, and proinsulin collected every 4-6 hours in fasting patients, accurately confirms the diagnosis of insulinoma in the majority of the patients. Once the diagnosis is confirmed, the next step in management involves identifying the location of the tumor and successfully removing it surgically. In the last two decades, clinicians have moved away from invasive angiography for preoperative localization. A multiphase computed tomography (CT) can be used to localize the lesion and evaluate for metastasis. If CT does not detect the lesion, selective arterial calcium stimulation test is recommended to identify the region of the lesion in the pancreas. Some argue that all preoperative localization techniques are superfluous. The combination of intraoperative ultra - sound and operative palpation has led to a nearly 100% success rate. Recently, in select cases, laparoscopic enucleations and resections of insulinomas have been performed with shorter length of stay and faster recovery time. Despite advances in imaging, a little over 10% of insulinoma patients undergo reexploration for missing lesions. Patients who are not candidates for tumor resections or awaiting surgery have had symptomatic relief from diazoxide and somatostatin analogs among various medical therapies. In patients with metastatic insulinoma, progression- free survival and overall survival are reported from newly approved chemotherapeutic agents. Liver-directed therapies, such as ablation and selective radiation, and cytoreductive surgery have also been performed for symptom control and prolonging survival.