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This information is about a rare group of neuroendocrine tumours (NETs)| called gastroenteropancreatic tumours (GEPs).
NETs are a rare group of tumours that start in the cells of the neuroendocrine system.
The neuroendocrine system is a network of endocrine glands and cells throughout the body. Endocrine glands produce and release hormones that circulate around the body. The hormones control the levels of particular chemicals and fluids in the body and help us to respond to changes in our environment.
Neuroendocrine tumours can be non-cancerous (benign) or cancerous (malignant). This information is about malignant types of neuroendocrine tumours affecting the digestive system.
The digestive system
View a large copy of the digestive system image|
When a tumour develops in part of the neuroendocrine system, it often causes too much of a certain hormone to be made. The type of hormone being overproduced depends on the type of gland that is affected by the tumour.
Some tumours don't cause any overproduction of any hormones and may not cause any symptoms. These are known as non-functioning NETs.
Many of these tumours are very slow-growing and may even appear to stop growing for a long time.
NETs are classified according to:
Most gastroenteropancreatic tumours (GEPs) develop in the digestive system. They usually start in the cells of the stomach (gastro), bowel (entero) or pancreas.
GEPs are named after the cells where they develop. These include:
Sometimes the primary site (where the cancer started) cannot be found. In this situation, the cancer may be found when it has spread to a different part of the body, such as the liver, and has formed a secondary tumour (metastasis).
The exact cause of GEPs is unknown. However, the risk of developing one is increased in people with Multiple Endocrine Neoplasia 1 and 2 (MEN 1| and MEN 2|). These conditions are usually caused by inherited faulty genes. The affected person may develop tumours in several different endocrine organs. MEN 1 and MEN 2 can affect both males and females. Genetic testing can be carried out for people with a family history of MEN.
The signs and symptoms depend on where the tumour is in the body and whether it is producing extra hormones.
It's important to remember that many symptoms of tumours of the neuroendocrine system are the same as symptoms of other, non-cancerous conditions.
Insulinomas can occur in any part of the pancreas. The pancreas produces insulin, which controls the level of sugar in the blood. An abnormally high level of insulin in the body causes low blood sugar levels (hypoglycaemia).
A low blood sugar level may cause symptoms such as:
A low blood sugar level is most likely to occur first thing in the morning, when exercising or after missing a meal. You can often raise your blood sugar level again by eating or by having a sugary drink.
Gastrinomas usually start in the pancreas or the upper part of the small bowel (duodenum). They may produce too much gastrin. Gastrin is a hormone that causes gastric acid to be made. High levels of gastric acid can lead to ulcers in the stomach, gullet (oesophagus) and the small bowel. There may be several ulcers, which often don't respond well to normal doses of the usual ulcer medicines. This is often called Zollinger-Ellison syndrome.
Common symptoms can include:
Glucagonomas occur most often in the pancreas. Glucagonomas usually produce too much glucagon. Glucagon is a hormone that has a role in controlling blood sugar levels.
VIPomas usually occur in the pancreas. They can produce too much of a substance called vasoactive intestinal peptide.
Somatostatinomas are extremely rare tumours that usually occur in the pancreas or parts of the small bowel (the duodenum or jejunum).
GEPs can be difficult to diagnose. Your doctor will ask you about your past medical conditions and about your symptoms.
You will also have tests. These may include any of the following:
Samples of blood and urine are taken to look for the levels of particular hormones. You may be asked to collect all the urine you pass in a 24-hour period. You may need to fast overnight before having certain blood tests. Some tests may be repeated to monitor any ongoing changes in hormone levels.
A combination of x-rays and scans will be taken to find where the tumour is and if it has spread.
This uses sound waves to build up a picture of the digestive system. You'll usually be asked not to eat or drink anything for at least six hours before the scan. Once you are lying comfortably on your back a gel is spread onto your abdomen. A small device that produces sound waves is then rubbed over the area. The sound waves produce a picture on a computer. The test is painless and only takes a few minutes.
The doctor passes a thin flexible tube called an endoscope into your mouth, down your throat and into your digestive system. An ultrasound is attached to the end of the endoscope. This enables the doctor to examine your digestive system organs more closely.
This test may be used to find where the cancer started (the primary tumour) or to check for any spread of the disease (secondaries or metastases).
GEPs often absorb a substance called octreotide. A small amount of octreotide is 'labelled' with a mildly radioactive tracer to make it show up on scan pictures. The octreotide is then injected into the bloodstream and taken up by the tumours wherever they are.
You have three scans: one on the day of the injection and two more over the next two days. This involves lying still while the scanner takes pictures. Each scan takes up to about an hour and a half. You will be able to go home between scans.
Sometimes MIBG, a substance that may also be absorbed by GEPs, is used for the scan. It is also made mildly radioactive for the scans which are done in a similar way to an octreoscan.
The dose of radioactivity from these scans is very low (about the same amount you get from an x-ray). And almost all of it leaves your body within a week. But if you are planning to travel abroad within three months of the scan let the doctor in the scanning department know. They may give you a letter to show to customs officials. This is because ports and airports have very sensitive radiation detectors which may pick up tiny amounts of radioactivity.
A CT scan takes a series of x-rays that build up a three-dimensional picture of the inside of the body. The scan is painless and takes 10–30 minutes. CT scans use small amounts of radiation, which are very unlikely to hurt you or anyone you come into contact with. You'll be asked not to eat or drink for at least four hours before the scan.
You may be given a drink or injection of a dye that allows particular areas to be seen more clearly. For a few minutes, this may make you feel hot all over. If you are allergic to iodine or have asthma you could have a more serious reaction to the injection, so it's important to let your doctor know beforehand.
This test is similar to a CT scan but uses magnetism, instead of x-rays, to build up a detailed picture of areas of your body. Before the scan you may be asked to complete and sign a checklist. This is to make sure it’s safe for you to have an MRI scan.
Before having the scan, you’ll be asked to remove any metal belongings, including jewellery. Some people are given an injection of dye into a vein in the arm. This is called a contrast medium and can help the images from the scan show up more clearly. During the test you will be asked to lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It is painless but can be slightly uncomfortable, and some people feel a bit claustrophobic during the scan. It’s also noisy, but you’ll be given earplugs or headphones. You'll be able to hear, and speak to, the person operating the scanner.
A PET scan uses low-dose radioactive sugar to measure the activity of cells in different parts of the body. Areas of cancer are usually more active than normal tissue and show up on the scan. You might have to travel to a specialist centre to have a PET scan. They are not always routinely used as specialists have different opinions as to whether they are more helpful than other investigations.
A small sample of cells is taken from the tumour (biopsy) to be examined under a microscope. The biopsy may be taken using ultrasound or CT scans to make sure that the sample is taken from the tumour. Depending on which part of the body is affected, you will be given a local or general anaesthetic.
Treatment depends on a number of factors including your general health and the position and size of the tumour.
Before you have any treatment, your doctor will give you full information about what it involves and explain its aims. They will usually ask you to sign a form saying that you give permission (consent) for the hospital staff to give you the treatment. No medical treatment can be given without your consent.
If the tumour is contained in one area (localised) or if there has been only limited spread, surgery| is usually the first choice of treatment. If it's possible to remove the tumour completely, no other treatment may be necessary.
If the tumour has spread to other parts of the body (metastatic), you may still have surgery to remove the part of the tumour that is producing too many hormones. This is often referred to as tumour debulking.
If a GEP is blocking an organ, such as the bowel, surgery may be helpful to relieve the blockage (obstruction).
If the tumour has spread to the liver, surgery can be used to remove the parts of the liver containing it. Very occasionally, a liver transplant may be considered for people with a particularly slow-growing tumour affecting the liver.
Somatostatin analogues are drugs used to control certain symptoms that GEPs can cause. They work by blocking the release of specific hormones. Commonly used somatostatin analogues are octreotide (Sandostatin®) and lanreotide (Somatuline® LA, Somatuline Autogel®).
Octreotide is given as a short-acting injection under the skin (subcutaneously) up to three times a day. You, or a family member, can be taught to give the injection. Longer-acting injections of octreotide or lanreotide can also be given. These injections are given deep under the skin, from once a week to once every four weeks, depending on the drug used and the situation. Somatostatin analogues may be given in combination with interferon.
This is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. It may sometimes be used to treat GEPs that are fast-growing or have spread. Chemotherapy| can help reduce the size of the tumour and lower the levels of hormones they produce.
Chemotherapy is often used for GEPs of the pancreas. However, as these may be very slow-growing tumours, your doctor may not think it is appropriate to use chemotherapy if your situation appears to be stable.
Sometimes blocking the blood supply to the tumours can slow down the growth of GEPs. This is called embolisation. A temporary tube is put into the artery that provides the blood supply to the tumour, and then a substance is injected to block the artery. This can be particularly useful for people with slow-growing tumours affecting the liver.
Interferon alpha| is a biological therapy, which can be used to treat the symptoms of GEPs. Interferon is a protein that occurs naturally in the body in small amounts. When given as a drug it can stimulate the body’s immune system to destroy cancer cells. It is given as an injection under the skin. At first it can cause flu-like symptoms such as chills, fever, aching joints and tiredness but these usually disappear. It may be given in combination with somatostatin analogues.
Targeted radiotherapy| may be used to reduce the number of tumour cells and the symptoms of GEP tumours. A radioactive substance is taken as a drink or injected into the bloodstream and goes directly to the tumour. There are two types of targeted treatments called MIBG and octreotide.
This treatment only works for tumours that absorb large amounts of either octreotide or MIBG. Before having it you have a scan that measures how much of the substance (octreotide or MIBG) is absorbed by the tumour.
In radionuclide therapy the radiation is used to kill the cancer cells, so a dose higher than that needed for a scan is used. Almost all of the radiation is absorbed by the tumour and very little goes to normal healthy tissues. That is why it’s called targeted therapy.If you have targeted radiotherapy, you may need to be in a room by yourself for a few days, so that other people around you are not unnecessarily exposed to the radiotherapy.
Some people have tummy ache or feel sick with the treatment but this can be relieved with medication. You may have a temporary drop in the levels of some of your blood cells. If this happens you may feel tired, be more at risk of infection, or bruise or bleed more easily. For most people side effects don’t last long and they recover quickly.
Radiofrequency ablation| may be used to treat tumours in the liver. It uses lasers or radiowaves (microwaves) to destroy the cancer cells by heating them to high temperatures. You are given a sedative to make you feel drowsy and relaxed. The doctor uses a local anaesthetic to numb the skin on your tummy (abdomen). A fine needle is then inserted through the skin over the liver and into the centre of the tumour. Powerful laser light or radiowaves are passed through the needle and into the tumour, which heats the cancer cells and destroys them.
You will probably stay in hospital overnight. You may feel sick, have tummy (abdominal) pain and a high temperature for a few days afterwards. Your doctor or nurse can give you more information.
If you produce too much stomach acid you may be given medicines to reduce this. Other drugs may be used to control your blood sugar or to control diarrhoea.
Research into treatments for GEP tumours is ongoing and advances are being made. Cancer doctors use clinical trials| to assess new treatments.
You may be asked to take part in a clinical trial. Your doctor will discuss the treatment with you so that you have a full understanding of the trial and what it means to take part.
Having investigations and treatment for cancer can be a very stressful experience. You may have many emotions| including anxiety, anger and fear. These are all normal reactions and are part of the process many people go through in trying to come to terms with their condition.
Many people find it helpful to talk things over with their doctor or nurse, or with one of our cancer support specialists|. Close friends and family members can also offer support.
This section has been compiled using information from a number of reliable sources including:
For answers, support or just a chat, call the Macmillan Support Line free (Monday to Friday, 9am-8pm)
If you have any questions about cancer, need support or just want someone to talk to, ask Macmillan.