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 a 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 are found in the stomach and small bowel but can occur anywhere along the GI tract.
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 known 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:
- Fever and sweating at night
- Discomfort or pain in the abdomen or around organs
- Painless lump in the abdomen
- Feeling sick and vomiting
- Weight loss
- Blood in stools or vomit
- Anaemia (low level red blood cells)
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.
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 best course of action for you is based on the risk category you are put in for your GIST coming back, this is called a recurrence. Unfortunately, some people are diagnosed with GIST when it has already spread to other parts of the body. You can find out more about this here.
The features that are currently used to determine the risk of the cancer coming back in patients with GIST or of the disease spreading to another part of the body are:
Size of the tumour
Large tumours are more likely to behave aggressively than smaller tumours. A small GIST removed when it is less than 2cm in size may not cause problems in the future.
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 and is an indicator to how aggressive the tumour is.
Tumours in the small bowel and rectum appear to be more aggressive than those occurring in the stomach.
If the surface of the tumour was damaged during the operation to remove it, or if the tumour was not intact at the time of the surgery, there is a chance that tumour cells may have escaped into the abdomen. Sometimes this alone will define the tumour as high risk.
The risk category you are in will affect your treatment and the number of follow-up appointments you have after treatment.
Your tumour should be sent for mutational analysis. There are two main sites of mutation, usually in a gene called KIT, and less commonly in a gene called PDGFRA. While the type of mutation does not routinely influence your treatment options, a mutation in PDGFRA may make the tumour resistant to the standard drugs to treat GIST. It is important to find out if your GIST is resistant to these drugs if drug treatment after surgery is being considered for you. Fortunately, tumours with a PDGFRA mutation are usually less aggressive than the more common ones with KIT mutation.
Some KIT mutant tumours (exon 9) respond better to larger dose of imatinib but treating exon 9 mutations in this way has not been approved in England and Wales.
Depending on where you live in the UK, you should be referred to a specialist sarcoma team for diagnosis and treatment.
In England and Wales, the National Institute for Health and Care Excellence (NICE) recommends that anyone with sarcoma should be referred to a specialist sarcoma team. In Northern Ireland, sarcoma is diagnosed and treated across a number of hospitals in Belfast. People in Scotland should be referred to the Scottish Sarcoma Service for treatment.
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, surgeon and other healthcare professionals involved in your care. They will support you throughout your treatment to ensure you get the right treatment as and when you need it.
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 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 because of the dangers of the procedure or because of the damage removing them would do to vital structures. Other treatment options are considered if this is the case for you.
Oral anticancer targeted drugs
Patients with tumours that are too large to be removed safely, or those that have already spread to other parts of the body, can be treated using targeted drugs.
85% of people with GIST have a change in the cells called a mutation. This mutation tells the GIST cells to grow and multiply and is essential to their survival. Targeted agents work by blocking the growth signals within the cancer cells generated by the mutation. The three targeted drugs that are used for GIST are Imatinib (Glivec®), Sunitinib (Sutent®) and Regorafenib (Stivarga).
Imatinib (Glivec) 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 (Sutent) is used as a second treatment option.
The drug 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.
The All Wales Medicines Strategy Group (AWMSG) has approved Regorafenib to treat people with a GIST in Wales.
The Scottish Medicines Consortium have approved Regorafenib for treating GIST in Scotland.
NICE has approved Regorafenib to treat people with a GIST in England.
Treatment before surgery
If the tumour was too large to be removed at the time of diagnosis, it may be treated be treated initially with a targeted drug like imatinib. If sufficient shrinkage has occurred after 6-12 months, it may be possible to do an operation both more safely and without the need to remove so much of the organ, like the stomach.
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 through the Cancer Drugs Fund.
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. Your oncologist should be able to advise you concerning the availability of a clinical trial for your particular situation.
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, for example, if you had a GIST in your stomach you will have needed to have part or most of your stomach removed. This will affect how you eat. 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:
- Feeling sick
- Swollen ankles
- Puffy eyes
- Itchy rash
Side effects of sunitinib can include:
- Skin rash and soreness
- Mouth ulcers
- High blood pressure
Side effects of regorafenib can include:
- Loss of appetite
- Weight loss
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 troublesome please speak to your sarcoma clinical nurse specialist or doctor.
A recurrence of GIST may be accompanied by cancer in other parts of the body. This is called metastasis or secondary cancer. Secondary cancers in GIST patients can appear anywhere but they most commonly occur in the abdomen and liver. They are treated with the targeted drugs imatinib and sunitinib. You will be monitored to see how your cancer is responding to these drugs and your follow up schedule will continue throughout your treatment.