Neuroendocrine Tumors of Gastroenteric or Pancreatic Origin (GEP-NET)

What are neuroendocrine tumors of gastroenteric or pancreatic origin (GEP-NET)?

Tumors are masses of accumulated abnormal cells that have grown out of control. They occur when genes that regulate normal cell growth are mutated or damaged, which leads to cells growing and dividing at an overaccelerated, unregulated pace. Neuroendocrine tumors of gastroenteric or pancreatic origin (GEP-NET), also sometimes worded as gastroenteropancreatic neuroendocrine tumors, are neuroendocrine tumors that appear in the gastrointestinal tract or the pancreas. Neuroendocrine tumors form from cells that release hormones into the blood in response to a signal from the nervous system. The gastrointestinal (GI) tract is a part of the digestive system, and is made up of the stomach, intestines, colon, and rectum. The pancreas is a gland that lies between the stomach and the front of the spine. It makes hormones and enzymes that help digestion.

What are the types and symptoms of GEP-NETs?

The GEP-NET tumors that appear in the lining of the GI tract are called carcinoids. About two thirds of GEP-NETs are carcinoids. They often grow slowly, and mostly occur in the small intestine, rectum, and appendix. Some carcinoids do not show any symptoms in early stages. For those that do, symptoms include:

• Abdominal pain
• Constipation
• Diarrhea
• Abnormally colored stool and/or blood in stool
• Nausea and vomiting
• Yellowing of the skin and eyes
• Heartburn
• Unintended weight loss
• Extreme tiredness

The other third of GEP-NETs are the tumors that appear in the pancreas: pancreatic neuroendocrine tumors, which are often referred to as islet cell tumors. Islet cells are cells that make hormones in the pancreas. Islet cell tumors are different from the usual form of pancreatic cancer, the majority of which are adenocarcinomas. The majority of islet cell tumors are benign, but some are malignant. Some don’t even cause any symptoms. For those that do, their symptoms can include:

• Back and/or abdominal pain
• Lump in the abdomen
• Indigestion
• Diarrhea
• Yellowing of the skin and eyes

Islet cell tumors can be functional (tumor in endocrine tissue that makes hormones) or nonfunctional (tumor in endocrine tissue that does not make extra hormones). Most islet cell tumors are functional tumors, and there are different kinds of them. The hormones these tumors create include: gastrin, insulin, glucagon, vasoactive intestinal peptides, and somatostatin. Signs and symptoms can be influenced by the specific hormone the tumor makes. These extra symptoms can include:

• Recurring stomach ulcers
• Low blood sugar
• Fast heartbeat
• Rash
• Sore mouth
• High blood sugar
• Blood clots
• Altered bowel habits
• Unintended weight loss
• Dehydration
• Gallstones

What causes GEP-NETs?

Normal, healthy cells grow at a steady rate, and die at a set time. However, sometimes healthy cells develop abnormalities; they grow and multiply at an out of control rate, and take much longer to die. When this happens to cells in the lining of the GI tract or the islet cells of the pancreas, they accumulate into a tumor there. Risk factors are anything that can increase a person’s chance of developing a disease. Risk factors for carcinoids are: having a family history of carcinoid syndrome and carcinoid heart syndrome. These can occur if the tumor spreads to the liver or other body parts. Risk factors for islet cell tumors are: MEN1 syndrome (multiple endocrine neoplasia type 1) and NF1 syndrome (neurofibromatosis type 1).

How are GEP-NETs diagnosed?

GEP-NETs can be diagnosed using a variety of procedures:

• Physical exam
• Thorough recording of patient and family history
• CT scans
• MRIs
• Endoscopic ultrasound
• Blood chemistry studies
• Tumor marker tests
• Urine scan
• MIBG scan
• Upper endoscopy
• Colonoscopy
• Biopsy

In the case of islet cell tumors that have a specific hormone affected, the following tests may be performed: Chromogranin A test, fasting serum gastrin test, basal acid output test, secretin stimulation test, somatostatin receptor scintigraphy, fasting serum glucose and insulin test, and fasting serum glucagon test. After diagnosis, doctors use the information obtained to assign a patient’s cancer a stage. This will help the doctor create the patient’s treatment plan. They do this by determining how large the tumor is, if it has spread to other parts of the body, and how far.

What are the treatments for GEP-NETs?

Treatment often depends on: location of the tumor in the GI tract/pancreas, tumor size, how far it’s spread, patient age and overall health, and whether the cancer has recently been diagnosed or is recurring. Treatment includes:

• Surgery
• Chemotherapy
• Radiation therapy
• Hormone therapy
• Targeted therapy
• Supportive care

In the case of GEP-NETs in the GI tract, treatment for carcinoid syndrome may also be needed. For islet cell tumors, hepatic arterial occlusion or chemoembolization may also be effective treatment.

Where can I find out more about GEP-NETs?

• NIH: Carcinoids
• NIH: Islet cell tumors
• Cancer Network