A GIST is a rare type of sarcoma found in the wall of the digestive system, most often in the stomach, but it can also grow in other parts. A soft tissue sarcoma is a type of cancer.
What is a GIST?
Gastrointestinal means the sarcoma starts in the digestive system (the gastrointestinal tract). Stromal means it develops from the interstitial cells of Cajal that play a role in the movement of the digestive system. These cells send signals to the muscles in the wall of the digestive system that help move food and liquid along. A tumour means a lump or growth in the body, which may or may not be cancer.
Most GISTs develop in the digestive system, but some start outside the digestive system in nearby areas such as the:
- large flat fatty tissue layer that covers the organs in the tummy (abdomen), also called the omentum
- thin lining of tissue that covers the organs and lines the inside of the tummy (abdomen), also called the peritoneum
Some GISTs behave in a non cancerous (benign) way. Generally, a tumour that behaves in a benign way tends to be relatively slow growing and is less likely to come back.
A tumour that behaves in a cancerous (malignant) way is faster growing and is more likely to come back or spread.
The larger the GIST, the more likely it is to behave like cancer. And if left untreated, a benign behaving tumour can start to act like a cancer.
Who gets GIST?
GISTs are most common in older people aged 60 to 65.
GISTs are linked with conditions such as:
- neurofibromatosis type 1
- Carney triad
- Carney-Stratakis syndrome
GISTs in children and adolescents are rare.
People with an early stage GIST often do not have any symptoms. So an early stage GIST may be found when people are having tests for other medical conditions. Most GISTs are diagnosed in later stages of the disease. The symptoms of an advanced GIST are likely to include:
- pain or discomfort in the tummy (abdomen)
- a feeling of fullness
- being sick
- blood in your stools or vomit
- feeling very tired
- a low red blood cell count (anaemia)
Treatment for GIST
Your treatment usually depends on the level of risk of your cancer, and your general health. Your doctor will look at several factors to decide whether your GIST is:
- very low risk
- low risk
- intermediate risk
- high risk
If your GIST is smaller than 2 cm, you might have an endoscopic ultrasound, usually with fine needle aspiration or core needle biopsy. Your surgeon might delay surgery until it grows bigger or you have symptoms. This is because small tumours are usually lower risk. But you will be followed up yearly. Your doctor might suggest this if it is an option for you.
For a GIST of more than 2 cm, surgery is usually the main treatment. Your surgeon aims to remove as much of the cancer as possible with a border of healthy tissue (clear margin) around it. Having a border of healthy tissue without any cancer cells is important as it lowers the risk of the cancer coming back.
Surgery might cure a smaller GIST. But it might not be possible for a surgeon to remove a larger GIST completely.
GIST can sometimes spread to other parts of the body. This spread is called a secondary or metastases. In some situations, it might be possible for a surgeon to remove these secondaries.
GIST in the stomach means your surgeon might need to remove all or part of your stomach. They may also need to remove your spleen. Surgery to the stomach is a big operation and it will take some time to adjust your eating afterwards. You will probably have to eat small, frequent meals (about two hourly) for quite a long time after the operation.
Targeted cancer drugs
Cancer cells have changes in their genes (DNA) that make them different from normal cells. These changes mean that they behave differently. Cancer cells can grow faster than normal cells and sometimes spread. Targeted cancer drugs work by ‘targeting’ those differences that a cancer cell has.
A type of targeted cancer drug used for GIST is called a tyrosine kinase inhibitor (TKI). Tyrosine kinase inhibitors (TKIs) block chemical messengers (enzymes) called tyrosine kinases. Tyrosine kinases help to send growth signals in cells, so blocking them stops the cell from growing and dividing.
Examples of TKIs used to treat GIST include:
- imatinib (Glivec)
- sunitinib (Sutent)
- regorafenib (Stivarga)
You might have imatinib to treat a GIST that can’t be completely removed with surgery, or which has spread before surgery.
Some people with GIST have a higher risk of their cancer coming back after surgery. This is called a high risk GIST. Imatinib can help to reduce the chances of the GIST coming back. So in this situation, your doctor may recommend you take imatinib for up to 3 years after your operation.
You may also have imatinib to shrink a GIST before surgery, so that your surgeon can remove it more easily. Sometimes a surgeon can completely remove a GIST after treatment with imatinib.
Protein testing for imatinib
Your doctor needs a sample of your GIST to carry our protein testing. This sample might be from when you had a biopsy to diagnose GIST, or an operation to remove the GIST. The cells are tested to see if they have a receptor on their surface called CD117.
This CD117 protein is made by a gene called c-kit. A fault in this gene causes the c-kit gene to make too much CD117 protein. Most GISTs have c-kit gene mutations.
If the GIST cells are CD117 positive, imatinib is likely to work very well. But it can work even for GISTs that are CD117 negative.
Your doctor might recommend that you have sunitinib (Sutent) in one of the following situations:
- imatinib has stopped working
- you have had severe side effects with imatinib treatment
You must have GIST that cannot be completely removed or has spread.
Regorafenib (Stivarga) is used to treat advanced GIST. Your doctor might recommend regorafenib if you have had treatment with imatinib and sunitinib and these drugs:
- have not worked
- or caused bad side effects
Advanced GIST means you cannot have surgery to remove the GIST, or it has spread. You must be fairly fit and well to have this drug.
Coping with a diagnosis of a rare cancer can be especially difficult, both practically and emotionally. Being well informed about your cancer and its treatment can make it easier to make decisions and cope with what happens.
Talking to other people
Talking to other people who have the same thing can also help.
Our discussion forum Cancer Chat is a place for anyone affected by cancer. You can share experiences, stories and information with other people who know what you are going through.
Some sarcoma organisations offer information and support, especially GIST Support UK. This is an organisation of people with GIST and their families