Neuroendocrine tumours (NETs)

If you have a NET, the levels of some chemicals in the blood may rise. This is mainly serotonin, 5HIAA and a protein called chromogranin A (CgA). 

Serotonin is a chemical the body makes that sends messages between different parts of the brain. It helps control lots of functions, such as how you sleep, your mood and your appetite

You will need to give blood samples to check the levels of these chemicals. You may be asked to fast (not eat) before these tests.

You may also have a blood test to look for hormones released by some NETs.

You will also have general blood tests to count the number of healthy blood cells in your blood. This is called a full blood count or FBC. You may have other blood tests to check how well your kidneys and liver are working, hormone levels, and your level of vitamin B12.

You may be asked to save all the urine you pass in a 24-hour period. Your doctor will then test it for 5HIAA.
5HIAA is made from serotonin by the liver and then passes out the body in the urine. Certain food, drinks and medicines can raise your levels of 5HIAA. You may need to avoid these for a few days before and during the collection.

An ultrasound scan uses soundwaves to build up a picture of inside your body. Usually, you cannot eat or drink anything for at least 6 hours before the scan. You may also have an ultrasound of your heart, called an echocardiogram.

A CT scan uses x-rays to build a 3D picture of the inside of the body.

An MRI scan uses magnetism to build up a detailed picture of areas of your body.

PET-CT scan
A PET-CT scan is a combination of PET and a CT scan. CT scans take a series of x-rays to build up a 3D picture. A PET scan uses low dose radiation to measure the activity of cells in different parts of their body.
PET-CT scans give more detailed information about the part of the body being scanned.

Nuclear medicine scans use a small amount of a radioactive substance called a tracer. The tracer shows up on scan pictures. The dose of radioactivity from these scans is low. It is about the same amount you get from an x-ray.

During a biopsy, doctors take a small piece of tissue (or a sample of cells) from a tumour. They then look at it under a microscope. You have a local anaesthetic to numb the area before the sample is taken. Sometimes, you have a general anaesthetic for the biopsy. This depends on where the NET is in your body.

Localised and low-grade NETs may be completely removed with surgery. The aim of the operation is to cure the cancer. Sometimes, this type of operation is also possible if there has been only limited spread. This is called regional spread. Depending on where the NET is, it may be possible to remove it during an endoscopy.
An operation to remove all of the cancer may sometimes be possible for NETs that have spread to the liver. This will depend on where the tumours are in your liver. Your doctors will discuss this with you.

If it is not possible to completely remove the tumour, doctors may try to remove as much as possible. This is called debulking. It can improve your symptoms by relieving pressure on other parts of the body. It can also help to reduce symptoms caused by the over-production of a hormone.
Surgery can also help relieve symptoms of a NET that has spread to more distant sites in the body (metastatic). For example, if a tumour is blocking the small bowel, surgery can remove it or bypass the blockage. 

Some NETs are slow-growing and may not change for months or years. If a NET spreads but is not causing symptoms, you may not need treatment straight away. Your doctor will monitor you with regular check-ups. If symptoms develop, you will have the option of treatment.

Somatostatin analogues are drugs that treat the symptoms of carcinoid syndrome. They work by blocking the hormones the tumour makes. They may also control the growth of NETs. You may be given them along with other treatments.

Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. You may have chemotherapy to treat NETs that have spread. The type of chemotherapy you will have depends on where the NET started in the body. Chemotherapy treatments that can be used for NETs include: capecitabine and temozolomide (CAPTEM), FOLFOX, streptozocin and fluorouracil (5FU), etoposide and cisplatin (EP), carboplatin and etoposide.

Targeted therapies are anti-cancer medicines that interfere with how cancer cells grow and divide. The two main targeted therapy drugs used are sunitinib (Sutent®) and everolimus (Afinitor®). You take these drugs as capsules or tablets. Other targeted therapies may be available as part of a clinical trial.

Interferon is a drug that can treat the symptoms of NETs. It may also control how the tumour grows. Interferon is a protein that you naturally have small amounts of in your body. If you have it as a drug, it can stimulate the body’s immune system to destroy cancer cells. You will have it as an injection under the skin.

Radiotherapy uses high-energy x-rays to destroy cancer cells, while doing as little harm as possible to normal cells. You may have radiotherapy if it is not possible to remove the tumour with surgery, or if it has already spread.

You may have radionuclide therapy to relieve symptoms of carcinoid syndrome and control the growth of NETs. This therapy uses a radioactive substance called a radionuclide. It is injected into the bloodstream.

A hepatic artery embolisation can sometimes shrink NETs in the liver. It can also relieve the symptoms of carcinoid syndrome. Hepatic artery embolisation works by reducing blood flow to the tumours. Tumours need a blood supply to survive.

Radiofrequency ablation (RFA) can treat NETs in the liver. It uses laser or radio waves to destroy the cancer cells by heating them to high temperatures. 

Selective internal radiation therapy is a type of cancer treatment that uses tiny radioactive beads. It can treat NETs that are found in the liver.

Below is a sample of the sources used in our neuroendocrine tumours (NETs) information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

Esmo clinical practice guidelines: endocrine and neuroendocrine cancers. Available from: www.esmo.org/guidelines/endocrine-and-neuroendocrine-cancers (accessed May 2021).

Reviewers
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Paul Ross, Consultant Medical Oncologist.

Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information

This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.