Definition

GIST is a type of sarcoma, rare cancers that develop in the connective tissues: muscle, bone, nerves, cartilage, tendons, blood vessels and the fatty and fibrous tissues. GIST is the most common type of sarcoma. It develops in the gastrointestinal (GI) tract, a long tube running through the body from the oesophagus (gullet) to the anus (back passage) and includes the stomach and intestines. 

Most GISTs occur because a change in the cells (mutation) tells the GIST cells to grow and multiply. There are also a number of rarer types of GIST:

  • Wild-type GIST: A type of GIST that is not caused by a KIT or PDGFRA cell mutation
  • Paediatric GIST: A GIST affecting children and young adults. Paediatric GIST is very rare  
  • Syndromic GIST: A type of GIST linked to Carney’s Triad Syndrome and Carney-Stratakis Syndrome and Neurofibromatosis.   
  • Familial GIST: A rare inherited form of GIST

Signs and symptoms

Symptoms of GIST can vary depending on the size and location of the tumour. They may include:

• Blood in your poo or vomit
• Anaemia (low level red blood cells)
• Fatigue
• Fever and sweating at night
• Discomfort or pain in your tummy
• Painless lump in the tummy
• Feeling sick and vomiting
• Weight loss

Types of diagnostic scans

A diagnosis of GIST may start with a visit to your GP who will examine you and then refer you to a specialist doctor. Some GISTs are discovered through investigations for another medical condition or are diagnosed after surgery. A specialist doctor will diagnose GIST through a series of tests. These may include:

  • Clinical examination – looking at or feeling any lump
  • A scan – taking pictures of the inside of the body
  • A biopsy – taking and testing a sample of tissue

A clear diagnosis will be made after a pathologist with experience in GIST has examined a tissue sample.

Scans and tests

CT

The Computerised Tomography (CT) scan takes a number of x-rays to make a 3D image of an affected area.

Ultrasound scan

Ultrasound uses sound waves to create images of the organs inside the body

Endoscopy

A thin, flexible telescope called an endoscope is passed through the mouth to the stomach and small bowel. The tip of the endoscope contains a
light and a tiny video camera so the doctor can see any abnormalities. The endoscope is sometimes used to take biopsies which will then be sent to a
laboratory to be tested. 

EUS

The EUS uses an endoscope with an ultrasound scanner attached to investigate tumours like GIST below the lining of the stomach or upper small bowel.

PET

The Positron Emission Tomography (PET) scan shows up changes in tissues that use glucose as their main source of energy. It involves an injection of a small amount of radioactive glucose into the body. The drug travels to places where glucose is used for energy and shows up cancers because they use glucose in a different way from normal tissue.

MRI

Magnetic Resonance Imaging (MRI) uses magnets to create an image of the tissues of the body. Histopathology Examination of a tissue sample by a pathologist
under a microscope to identify disease.


Blood test

Your doctor may check for anaemia which could be a sign of bleeding in the GI tract.

Understanding the diagnosis

Your doctor will use the results of your scans and tests to diagnose you with a GIST and advise you on treatment options. The treatment for you is based on the risk category you are put in for your Your risk category could be high, intermediate or low. This is worked out by looking at: 

Size of the tumour

Large tumours are more likely to behave aggressively than smaller tumours. 

Mitotic count

Mitotic count is the number of actively dividing cells seen under a microscope within a certain area of the tumour. This tells the doctors the rate at which the cancer cells are multiplying, which shows how aggressive the tumour is.

Location

Tumours in the small bowel and back passage are more aggressive than those in the stomach.

Tumour rupture

Sometimes the surface of the tumour can be damaged during the operation to remove it. In other cases the tumour may not be intact at the time of the surgery. In these cases there is a chance that tumour cells may have escaped into the abdomen, which can put you at a higher risk of your GIST coming back.

Mutational analysis

When your tumour is removed it should be sent for mutational analysis. This test finds out what mutation has caused the GIST.

There are two main sites of mutation in GIST:

• In a gene called KIT
• In a gene called PDGFRA

KIT is more common. However if your GIST is caused by a PDGFRA mutation it may affect your treatment options. This is because the drugs used to treat GISTs may not work properly on GISTs caused by a PDGFRA mutation.

Treatment

Anyone with a GIST should be referred to a specialist sarcoma team for diagnosis and treatment.

The care of GIST patients should be supervised by cancer specialists with experience in GIST. Your sarcoma team will work alongside a specialist gastrointestinal team. Your case will be managed by a team of experts from a wide range of health care professions called a multidisciplinary team (MDT). Your MDT will include your key worker or sarcoma clinical nurse specialist, GI surgeon and other healthcare professionals involved in your care.

Types of treatment

The type of treatment you receive depends on what part of the GI tract it is in and the risk category of recurrence. Your MDT will discuss your case and your doctor or nurse will talk you through your options so you are included in deciding what treatment is best for you.

Surgery

Surgery is usually the first treatment method used for GIST. The surgeon will remove the tumour and will aim to take out an area of normal tissue too. This is known as taking a margin. It allows cancer cells that are not visible to the naked eye to be removed along with the tumour. This can reduce the risk of the cancer coming back.

GIST in the small bowel
You may have an operation to remove part of the small bowel. This usually doesn’t have any long-lasting side effects.

GIST in your stomach
You may need to have part or most of your stomach removed. This will affect how you eat. Specialist dietitians can give you advice and support on making changes to your diet.

Some tumours cannot be removed surgically. Other treatment options are considered if this is the case for you.

Oral anticancer targeted drugs
If your tumour is too large to be removed safely, or your GIST has already spread to other parts of the body, it can be treated using targeted drugs. Most people with GIST have a change in the cells called a mutation. This mutation tells the GIST cells to grow and multiply. Targeted drugs work by blocking the growth signals, causing the GIST to stop growing and shrink. The three targeted drugs that are used for GIST are Imatinib, Sunitinib, and Regorafenib.

Imatinib is the first treatment choice for GIST patients. It is effective in 80% of patients and on average will control the disease for about two years. Sometimes the tumour develops a resistance to imatinib and hence over time it stops working. If this happens, sunitinib is used as a second treatment option.

Regorafenib (Stivarga) is used to treat people who have GIST that cannot be operated on or has spread to another part of the body. If you have had treatment with Imatinib and Sunitinib that has not worked or has caused bad side effects, then Regorafenib is an alternative treatment. 

Treatment with these drugs may harm your fertility. Please speak to your doctor or clinical nurse specialist about your options for preserving fertility before treatment. It is not advised to become pregnant, breastfeed or father a child when on these treatments.

Treatment before surgery

If the tumour was too large to be removed at the time of diagnosis, it may be treated by a targeted drug like imatinib. If enough shrinkage has occurred after 6–12 months, it may be possible to do an operation more safely.

Treatment after surgery

Some people who have had their tumour removed but are at a high risk of the cancer coming back may have a treatment called adjuvant therapy. Adjuvant therapy is an additional treatment after the first treatment which reduces the risk of the cancer returning. 

Clinical trials suggest that if it is to be used, giving it for three years is likely to give the best results. Using imatinib as an adjuvant therapy has been approved for use in certain
circumstances in Scotland by The Scottish Medicines Consortium (SMC). Adjuvant imatinib is currently available in England and Wales via the Cancer Drugs Fund.

Clinical trials

You may be offered the opportunity to take part in a study to investigate new diagnosis methods, drugs and treatments. Some studies also look at the care and well-being of patients.
Your doctor or nurse can give you more information on opportunities for you to take part in a clinical trial.

A number of clinical trials are underway looking at new drugs that may overcome some of the limitations of the existing drugs used to treat GIST. Some clinical trials are trying to find better ways of using the drugs already available. Ask your doctor for more information on clinical trials, or take a look at our Clinical Trials Hub

Side effects of treatment

You may experience side effects from your treatment. If you have had surgery for GIST it may have some lasting impact on your eating habits. Specialist dieticians can give you advice and support on making changes to your diet. Support and information on diet should be available to all patients who have had major abdominal surgery.

Imatininb and sunitinib are strong drugs that can often cause side effects.

Side effects of imatinib can include:

  • Tiredness
  • Feeling sick
  • Diarrhoea
  • Swollen ankles
  • Puffy eyes
  • Itchy rash

Side effects of sunitinib can include:

  • Skin rash and soreness
  • Tiredness
  • Mouth ulcers
  • High blood pressure

Side effects of regorafenib can include:

  • Tiredness
  • Loss of appetite
  • Diarrhoea
  • Weight loss
  • Pain

These side effects can be treated by other medicines and your sarcoma clinical nurse specialist can give you advice and support on managing the effects of taking imatinib and sunitinib. If your symptoms continue or are getting worse, please speak to your sarcoma clinical nurse specialist or doctor.

Recurrence

After your treatment is finished you will have follow-up appointments for several years. This is where your doctor can look for signs of your GIST coming back. At follow up appointment you will have:

• A chance to discuss symptoms
• An examination to look for any signs of GIST returning such as a CT or MRI scan

If your GIST does come back a new treatment plan will be put in place for you.

GISTs can spread to other parts of the body. This is called metastasis or secondary cancer. Secondary cancers in GIST patients can appear anywhere but are more common in the abdomen and liver. You will be treated with the targeted drugs imatinib and sunitinib. During treatment you will be monitored to see how your cancer is responding to these drugs. You should get support from your sarcoma clinical nurse specialist on managing symptoms and side effects.