Fluorodopa F 18 in Congenital Hyperinsulinism and Insulinoma

Overview

Low blood sugars are known to cause brain damage in newborn babies. One of the most common causes of low blood sugars persisting beyond the new born period is a condition called congenital hyperinsulinism (HI). This is a disease whereby the pancreas secretes too much insulin and causes low blood sugars. Twenty to forty percent of these babies will have brain damage. There are two forms of this disease. In one form only a small part of the pancreas makes too much insulin (focal HI) and in the other, the whole pancreas make too much insulin (diffuse HI). Another very similar disease is insulinoma which occurs after birth, but also causes hyperinsulinism. If a surgeon could know which part of the pancreas has the focal lesion he could remove it and cure the patient. The purpose of this study is to investigate whether a new investigational drug called Fluorodopa F 18, when used with a PET scan, can find the focal lesion and guide the surgeon to remove it, thus curing the patient and preventing further brain damage.

Congenital Hyperinsulinism (HI) is a disorder of insulin secretion that causes profound hypoglycemia leading to significant morbidity. It is the most common form of persistent neonatal hypoglycemia, and the most dangerous. Inappropriate insulin secretion causes not only hypoglycemia but also inability to release free fatty acids from adipose tissue and inability to release glycogen from the liver. Hence the brain is deprived of all the major fuel sources (glucose, beta-hydroxybutyrate and lactate) for energy thus leading to the high incidence of brain damage. In up to 50% of cases of congenital hyperinsulinism, medical therapy fails and surgical resection of the pancreas is necessary. Previous techniques developed to differentiate those patients with focal HI in whom surgery could result in a cure are very invasive and put the infants at risk for hypoglycemic brain damage or arterial thrombosis. It is known that the beta cells in the pancreatic islets, similar to other neuroendocrine tissues, contain amino acid decarboxylase (AADC). Beta cells take up L-Dopa and convert it into dopamine by AADC. It was proposed that as other neuroendocrine tumors such as phaeochromocytoma and carcinoid tumors express AADC and can be very easily visualized using Fluorodopa F 18 PET then so also would the pancreas be easily and accurately visualized. After initial reports demonstrated the effectiveness, safety and accuracy, there have been now over 200 patients with HI reported in the literature who have had Fluorodopa F 18 PET scans with suggestions that referral to major HI centers for Fluorodopa F 18 PET CT is now an integral part of standard of care management of patients with HI that require surgery. Fluorodopa F 18 PET scanning for patients with Hyperinsulinism is now established in Europe and Australia, and has close to 95% sensitivity. When linked to Computed Tomography (CT) image of the pancreas, Fluorodopa F 18 PET allows the surgeon to image the pancreas in three dimensions, to even more accurately identify the site of the focal lesion, increasing the chance of a sufficient partial pancreatectomy to cure the patient. Similarly, insulinomas are neuroendocrine cell tumors that are typically benign (90%) and very rare occurring in 1-4 per million of the population with \> 50% occurring in adults \>age 25 years. Biochemical differentiation of insulinomas from congenital hyperinsulinism may be aided by the use of the pro-insulin:insulin ratio, by the age of presentation and by the history. The standard of care for insulinoma is to remove them once identified, rather than long term medical treatment. Current imaging techniques include CT scan pancreas, endoscopic ultrasound of the pancreas and MRI pancreas however despite using these modalities in some patients the insulinoma may not be found. 18F-DOPA has been shown to be superior than MIBG scanning for neuroendocrine tumors such as phaeochromocytoma, but there is very little data in patients with insulinoma. Moreover, patients with MEN 1 and insulinoma may have more than one tumor, which if missed with conventional imaging could result in failure to cure with surgery. The objectives of this study are: 1. To determine, using Positron Emission Tomography, whether or not the uptake of a radiopharmaceutical agent, Fluorodopa 18F (18F-DOPA) produced in a cyclotron located at a distance far from the imaging center will produce qualitatively adequate pancreatic images in patients with congenital hyperinsulinism 2. To determine, using direct comparisons, whether or not Fluorodopa 18F Positron Emission Tomography (18F-DOPA PET) combined with Computed Tomography (CT) will produce pancreatic images matching the gold-standard of histopathological findings at surgery for partial or complete pancreatectomy in the treatment of patients with congenital hyperinsulinism 3. To determine, using direct comparisons, whether or not Fluorodopa 18F Positron Emission Tomography (18F-DOPA PET) combined with Computed Tomography (CT) will produce pancreatic images matching the gold-standard of histopathological findings at surgery for insulinomas 4. To determine the best way to interpret the 18F-DOPA PET scans comparing SUV max:SUV sub max at a ratio of the current 1.5, a suggested 1.3 and by using visual inspection of the images.