RECENT TRENDS IN MANAGEMENT OF INSULINOMA

Abstract

Insulinomas are well-differentiated pancreatic endocrinetumors causing symptomatic hypoglycemia due to secretion of insulin from β cellsof pancreas,with an incidence of 1–4cases per million per year(Bhatti et al., 2016). Most insulinomas are benign, small (<2 cm) tumors with only 10% of cases usually are malignant. They are usually solitary lesions distributed all over the pancreas, except if associated with MEN1 syndrome; they tend to be multifocal(Fernandez Ranvier et al., 2016). The clinical signs and symptoms of insulinomas are divided into 2 categories. Neuroglycopenic symptoms, which are caused as a direct result of hypoglycemia and may include weakness, confusion, visual disorders and in severe cases comas and seizures may occur. Autonomic symptoms, which are resulting from release of catecholamine due to hypoglycemia, involve palpitations,diaphoresis, tremors and anxiety (Fernandez Ranvier et al., 2016). The diagnosis of insulinoma depends on criteria of Whipple triad: (1) hypoglycemia (blood glucose level <50 mg/dL), (2) neuroglycopenic manifestations and (3) releive of symptoms promptlyafter administration of glucose. At present, biochemical measurement the levels of plasma glucose, C peptide,insulin, and proinsulin during a 72-hour fast test can discover up to 99% of insulinomas and has considered as the gold standard of diagnosis(Fernandez Ranvier et al., 2016). After confirmation of the diagnosis, the next involves localization of the tumor andsurgically removing it successfully(Luo et al., 2016). The role of preoperative imaging to evaluate evidence of metastatic disease and to detect the type of operation(Gahlot et al., 2011). Various modalities can be used for localization including transabdominal US, multiphase helical CT, MRI, and SRS, but when preoperative noninvasive studies fail to localize tumors, invasive studies may aid in localization such as Pancreatic arteriography, THPVS and SACS (Gahlot et al., 2011). Recently,clinicians have replaced the invasive angiography forpreoperative localization(Luo et al., 2016). IOUS can precisely demonstrate the correlation of tumor to the portal vein,pancreatic and common bile duct, splenic and superior mesenteric blood vessels (Gahlot et al., 2011). Currently the ideal method is IOUS with manual palpation which has a sensitivity of about 83- 98% (Luo et al., 2016). In recent years, a new receptor targeted imaging technique, GLP1R imaging, for detecting insulinoma has been established(Luo et al., 2016). Surgical resection is the ideal for insulinomas and had a cure rateover 90%of the patients. Surgical techniquesinvolve enucleation of the tumor, partial or total pancreatic resection, and pancreato-duodenectomy (Whipple’soperation). If malignancy is suspected, metastatic tumor resection and/or lymph node dissection is mandatory (Wei et al., 2016). In recent years, laparoscopic resection of pancreatic insulinomas has been successfully done and provides patients with the benefits of minimally invasive surgery and it can minimize time of operation, loss of blood, and morbidity, and involves a faster recovery period and shorter hospital stay for the patient (Liu et al., 2015). Insulinoma patients who are not surgical candidates can be managed with medical therapy and dietary adjustment to avoid fasting forlong duration. The initial ideal drug for patients with insulinoma is diazoxide, also other drugs can be used such as octreotide and everolimus (Taye and Libutti, 2015).