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What are neuroendocrine tumours?

The neuroendocrine system is a network of glands and nerve cells that make hormones and release them into the bloodstream. These hormones help control normal body functions, for example digesting food. 

Neuroendocrine cells are found throughout the body, but mainly in the gastro-intestinal tract (including large bowel and small bowel), pancreas and lungs.  

Neuroendocrine tumours (also referred to as NET) are an uncommon type of tumour that forms in these cells. The type is generally defined by where the abnormal cells come from and can range from low grade (slow growing) to high grade (fast growing). Neuroendocrine tumours that produce extra amounts of hormones can cause certain symptoms and are referred to as functional tumours. However, not all neuroendocrine tumour produce extra hormones (non-functional).  

There are several types of neuroendocrine tumours including: 

  • gastro-intestinal which start in the large and small bowel 
  • pancreatic which account for about 7% of neuroendocrine tumours 
  • lung 
  • merkel cell carcinoma which involves the Merkel cells in the top layer of the skin 
  • neuroblastoma which usually starts in the adrenal glands and affects immature or developing nerve cells in children. 

Neuroendocrine tumours are not common. It is estimated that 5178 new cases will be diagnosed in Australian in 2021. Neuroendocrine tumours are more common in people over the age of 40. Neuroblastoma is more likely in children under the age of five.  



Neuroendocrine tumours symptoms

Most neuroendocrine tumours develop slowly over several years but they can also be aggressive and grow quickly, spreading to other parts of the body and causing problems. 

In the early stages neuroendocrine tumours may not cause symptoms. If you do have symptoms, it will depend on where in the body the tumour is and if the tumour cells are producing hormones. You may experience general symptoms such as fatigue and loss of appetite. 

Gastro-intestinal neuroendocrine tumours 

Symptoms may include: 

  • abdominal (tummy) pain and bloating

  • changes in bowel or bladder habits, including diarrhoea 

  • bowel obstruction or bleeding from the anus  

  • facial flushing and asthma-like wheezing.

Pancreatic neuroendocrine tumours 

Symptoms may include:  

  • low blood sugar levels (hypoglycaemia) causing shaking, sweating, confusion, dizziness and rapid heartbeat  
  • high blood sugar levels (hyperglycaemia) which may cause increased urination, excessive thirst and blurred vision  
  • indigestion (heartburn) and stomach ulcers  
  • rash in the groin area  
  • unexplained weight loss  
  • nausea or vomiting  
  • changes in bowel habits, including diarrhoea or pale, foul-smelling stools that are hard to flush away. 

Lung  

Symptoms may include:  

  • repeated pneumonia or chest infections  
  • coughing up blood  
  • shortness of breath; wheezing  
  • chest pain.  

Merkel cell carcinoma  

This usually occurs as a painless hard nodule (tumour) in the skin that grows rapidly and is often red, purple or blue, or can be flesh-coloured. Some patients feel the nodule is under (rather than in) the skin. The most common location is skin that has been exposed heavily to the sun such as the face, head and neck. 

Neuroblastoma  

Symptoms may include:  

  • painless lump or swelling in the tummy, chest or neck  
  • swollen legs, arms, upper chest, neck and face  
  • loss of appetite or feeling full  
  • weight loss  
  • changes in bowel or bladder habits  
  • difficulty breathing or swallowing  
  • headaches or dizziness  
  • drooping eyelid  
  • trouble feeling or moving arms and legs. 


Causes of neuroendocrine tumours

The causes of most neuroendocrine tumours are not known. Some risk factors may include:  

  • genetic factors – some rare inherited diseases can put people at more risk of developing neuroendocrine tumours 

  • pre-existing conditions such as peptic ulcers or diabetes.



Diagnosis of neuroendocrine tumours

Neuroendocrine tumours can be difficult to find and are sometimes diagnosed when patients are undergoing tests for a different condition. 

If your doctor thinks that you may have a NET (or one of the syndromes associated with neuroendocrine tumours) they will take your medical history, perform a physical examination and carry out certain tests. If the results suggest that you may have a NET, your doctor will refer you to a specialist who will carry out further tests such as: 

Blood tests

Blood test will include a full blood count to measure your white blood cells, red blood cells and platelets and chromogranin A (a hormone marker). 

Urine test

Urine tests will be taken to measure serotonin production which can be produced by NETs.  

Endoscopy

In this test a flexible tube with a camera on the end (endoscopy) will be inserted, under sedation, down the throat into the stomach or the anus and large bowel to view your gut. 

Bronchoscopy

For a bronchoscopy, a thin, tube-like instrument with a light and lens for viewing (bronchoscope) is inserted through the mouth or nose to view your lungs.  

CT scan

Special machines are used to scan and create pictures of the inside of your body. You may have an injection of dye into your veins before the scan which makes the pictures clearer.  During the scan you will lie on a table which moves in and out of the scanner.  A CT scan takes about 10-30 minutes.  

MRI

An MRI scan produces detailed cross-sectional pictures of your body and can show the extent of any tumours.  You will lie on a table which slides into a large metal tube that is open at both ends. An MRI scan takes about 30-90 minutes.  

PET scan

Before having the PET scan you will be injected with a small amount of radioactive solutions. You will be asked to sit for 30-90 minutes so the solution can mover around your body.  Many cancer cells will show up brighter on the scan. The scan takes around 30 minutes.  

Biopsy

Biopsy involves the removal of some tissue from the affected area for closer examination under a microscopy. In a needle biopsy, you will have a local anaesthetic to numb the area and a small, thin tube in inserted into the tumour. In an open or surgical biopsy you will have general anaesthetic and a surgeon will cut through the skin to expose the affected area.  

Echocardiogram

An echocardiogram is a painless ultrasound which examines your heart valves which can sometimes be affected by NETs. This procedure takes around 30-60 minutes.  



Treatment for neuroendocrine tumours

Discussion with your doctor will help you decide on the best treatment for your tumour depending on the type of NET you have; the symptoms you have; where it is in your body; how far it has spread; your age, fitness and general health and your preferences. 

The main treatment options for neuroendocrine tumours include surgery, chemotherapy, targeted therapy, theranostics – peptide receptor radionuclide therapy (PRRT) and drug therapy (to control any symptoms caused by extra hormones). Merkel cell carcinoma may also be treated using radiotherapy. Treatments can be given alone, in combination or one after the other. This is called multi-modality treatment. If the NET is slow-growing and not causing any symptoms you may not need immediate treatment. 

Palliative care

In some cases of neuroendocrine tumours, your medical team may talk to you about palliative care. Palliative care aims to improve your quality of life by alleviating symptoms of cancer. 

As well as slowing the spread of neuroendocrine tumours, palliative treatment can relieve pain and help manage other symptoms. Treatment may include radiotherapy, chemotherapy or other drug therapies. 

Treatment Team

Depending on your treatment, your treatment team may consist of a number of different health professionals, such as:
  • GP (General Practitioner)- looks after your general health and works with your specialists to coordinate treatment.
  • Surgeon- surgically removes tumours and performs some biopsies.
  • Medical oncologist- prescribes and coordinates the course of chemotherapy.
  • Radiation oncologist- prescribes and coordinates radiation therapy treatment.
  • Nuclear medicine specialist- coordinates the delivery of radioactive scans and treatment.
  • Gastroenterologist- specialises in diseases of the digestive system.
  • Endocrinologist- diagnoses, treats and manages disorders of the endocrine (hormonal)system.
  • Lung physician - specialises in treating and managing patients who have diseases of the lung.
  • Cancer nurses- assist with treatment and provide information and support throughout your treatment.
  • Dietitian- recommends an eating plan to follow while you are in treatment and recovery.
  • Physiotherapist/occupational therapist- help with physical and practical problems such as restoring movement and mobility after treatment.
  • Other allied health professionals- such as social workers, pharmacists and counsellors..


Screening for neuroendocrine tumours

There is currently no national screening program for neuroendocrine tumours available in Australia. 



Preventing neuroendocrine tumours

As the causes of most neuroendocrine tumours are not understood there is no prevention advice specific to this disease.  



Prognosis of neuroendocrine tumours

It is not possible for a doctor to predict the exact course of a disease, as it will depend on each person's individual circumstances. However, your doctor may give you a prognosis - the likely outcome of the disease - based on the test results, the rate of tumour growth, as well as your age, fitness and medical history.  



Sources

Understanding Neuroendocrine Tumours (NETs). Cancer council Australia ©2021. Last medical review of this fact sheet: February 2021. 

Australian Institute of Health and Welfare (AIHW), Australian Cancer Incidence and Mortality (ACIM) books: Neuroendocrine tumours, AIHW, Canberra, 2018. 

This web-based resource was made possible by the Cancer Australia Supporting people with cancer Grant initiative, funded by the Australian Government.