Pancreatic Neuroendocrine Tumors
The pancreas is located in the upper part of the abdominal cavity behind the stomach, intestines and spleen. This organ serves two major functions: production of digestive enzymes and production of hormones.
Pancreatic tumors can arise from the cells that produce and transport digestive enzymes and from the cells that produce the wide variety of hormones released into the bloodstream. About 95 percent of pancreatic tumors arise from the cells associated with food digestion and are termed adenocarcinomas. The remaining 5 percent of tumors are neuroendocrine tumors, or tumors named for their ability to secrete hormones.
Neuroendocrine tumors overproduce hormones. Patients with these tumors often have a much better outcome than patients with pancreatic adenocarcinoma, and they may have good cure rates, depending on the type of tumor. Some neuroendocrine tumors are associated with genetic mutations, which can cause several members of the same family to have these types of tumors.
The rarity of these tumors makes the care of these patients challenging, but our multidisciplinary team offers patients access to many experts for treatment.
Types of Pancreatic Neuroendocrine Tumors
Insulin is produced by beta cells, which are organized into islands of cells in the pancreas. The primary function of insulin is to regulate the metabolism and storage of sugar in the body.
Insulinomas are neuroendocrine tumors that produce insulin and are the most common type of functional neuroendocrine tumors. As these tumors grow they produce large amounts of insulin, which can cause low blood sugar. When the blood sugar gets too low, patients can experience symptoms, such as dizziness, confusion, abnormal behavior and even loss of consciousness.
Several tests are required to confirm the diagnosis of an insulinoma, because there are several other reasons for low blood sugar. Once the diagnosis is confirmed with blood tests, imaging studies, such as a computed tomography (CAT) scan or an ultrasound, are used to find the location of the tumor. The primary treatment is surgical removal of the insulinoma, which provides excellent cure rates.
A gastrinoma is a neuroendocrine tumor that produces the hormone gastrin. Gastrin stimulates the stomach to produce acid and aids in the digestion of food. Normally, when there is enough acid in the stomach to digest a meal, the body naturally decreases the production of gastrin. After food has left the stomach and begins to enter the intestine, stomach acid level slowly returns to the level needed for an empty stomach.
Gastrinomas continuously produce gastrin, which leads to very high levels of stomach acid that can then lead to ulcer formation in the stomach and small intestine, also known as Zollinger-Ellison syndrome. Patients may complain of abdominal pain from these ulcers, which may improve with antacid medications.
Blood tests to measure the level of gastrin can be falsely elevated if patients are taking antacid medications during tests, so these should be discontinued prior to testing. After the diagnosis of gastrinoma is confirmed with blood tests, imaging studies, such as CAT scan or an ultrasound can help find the location of the tumor prior to surgical removal.
The alpha cells of the pancreas produce the hormone glucagon, which acts to counter the effects of insulin. Normally, when a person has not eaten for several hours, blood sugar drops and glucagon is released. This causes the breakdown of sugar stored in the form of glucagon, which quickly brings the blood sugar back up to normal.
Glucagonomas continuously produce glucagon, causing continuously elevated blood sugar and symptoms typically seen with diabetes. After imaging studies are completed, surgical removal of the tumor is performed.
Vasoactive intestinal polypeptide (VIP) is a hormone produced in the pancreas and in other locations throughout the body. Neuroendocrine tumors, or VIPomas, will cause symptoms such as profuse, watery diarrhea; dehydration; and electrolyte disturbances.
These tumors are extremely rare, and blood tests and imaging studies are needed to confirm the diagnosis. Patients are treated with medication to decrease symptoms and often require intravenous fluid to treat dehydration before proceeding to surgery.
Nonfunctional Neuroendocrine Tumors
Some tumors that arise from endocrine cells of the pancreas do not produce hormones and therefore do not produce any of the symptoms described above. These types of tumors are often detected incidentally on computed tomography (CT) scan or other imaging studies obtained to test another medical problem.
Some tumors may grow quite large and cause upper abdominal discomfort as they compress surrounding structures. The challenge in the diagnosis of these types of tumors is to distinguish them from pancreatic adenocarcinoma, which has a worse prognosis. After blood tests and imaging studies are completed, surgery is the primary treatment for nonfunctional neuroendocrine tumors.
Treatment of Pancreatic Neuroendocrine Tumors
The treatment of pancreatic neuroendocrine tumors requires a multidisciplinary approach with medical, surgical, oncologic and radiological treatments. Medical management is often used to control symptoms caused by tumor hormone production prior to surgery. Chemotherapy and radiation therapy are aimed at decreasing recurrence rates and controlling symptoms in patients with metastatic or unresectable tumors.
The Neuroendocrine Tumor Program at Montefiore Einstein Center for Cancer Care provides patients with an expert level of care across all these disciplines.