Gastrointestinal stromal tumours (GISTs) are rare cancers that develop in the digestive system. They are a type of soft tissue sarcoma.
Most GISTs start in the stomach or small bowel. But they can develop anywhere along the length of the digestive system, including in the:
- gullet (oesophagus)
- and back passage (rectum).
Very rarely, they can develop outside the digestive system.
Every year, about 900 people in the UK are diagnosed with a GIST. They are most common in people aged 50 to 60. They are rare in people under the age of 40.
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The symptoms you have depend on the size of the tumour and where it is in the digestive system. Symptoms may include:
- discomfort or pain in the tummy (abdomen)
- blood in your poo (stools) or vomit
- anaemia (low level of red blood cells)
- a painless lump in the tummy
- being sick (vomiting)
- fatigue (tiredness and a feeling of weakness)
- a high temperature (fever) and sweating at night
- unexplained weight loss.
These symptoms can be caused by conditions other than a GIST, but you should always have them checked by your doctor.
Some people do not have symptoms but are diagnosed by chance when having a test or scan done for another reason.
The causes of GISTs are unknown, but research is happening to try to find out more.
Most people who have a GIST do not have a family history of the condition. But there are very rare cases where several family members have been diagnosed with a GIST.
People with a condition called neurofibromatosis (NF) have a slightly increased risk of developing a GIST.
Tests and diagnosis
If you have symptoms, you usually start by seeing your GP, who will examine you. If your GP is not sure what the problem is, or thinks your symptoms could be caused by cancer, they will refer you to a specialist doctor at the hospital.
You may also have blood tests to check your general health and the number of cells in your blood (blood count).
At the hospital, the specialist doctor will ask you about your symptoms and your general health. They will also examine you and arrange some of the following tests.
Our cancer support specialists or your specialist doctor or nurse can give you information about any tests we do not explain here.
Endoscopy or colonoscopy
These tests use a thin tube called an endoscope to look inside the gullet, stomach and bowel. For an endoscopy, the doctor passes a thin tube called an endoscope down the throat and into the stomach and small bowel. If you have a colonoscopy, the doctor gently passes the endoscope into the back passage (rectum) to look at the large bowel.
Endoscopic ultrasound (EUS)
An endoscopic ultrasound uses an endoscope with an ultrasound probe at the end. The probe uses soundwaves to make a picture of the inside of the stomach and the surrounding area. It can help show the size and position of the tumour.
Your doctor or nurse may take samples of tissue from the tumour. The samples are looked at under a microscope. This is called a biopsy. If you are going to have surgery to remove the tumour, you may not have a biopsy taken before your operation. Instead, the tumour is sent to the laboratory after the operation for tests to confirm that it is a GIST.
The grade of a cancer gives an idea of how quickly it might grow. Doctors look at a sample of the cancer cells under a microscope to find the grade of the cancer.
For GISTs, the grade is based on the rate the cancer cells are dividing at to make new tumour cells. This is called the mitotic rate. There are two grades:
- G1 (low grade) – the cancer cells have a low mitotic rate, they are growing slowly and less likely to spread.
- G2 (high grade) – the cancer cells have a high mitotic rate, they are growing faster and more likely to spread.
The stage of a cancer describes its size and whether it has spread beyond its original site. Knowing the stage of the cancer helps your doctors decide on the best treatment for you.
Different staging systems may be used. Two of the most commonly used systems for staging GISTs are the TNM staging system and a number staging system.
TNM stands for Tumour, Node and Metastasis.
- T describes the size of the tumour.
- N describes whether the cancer has spread to the lymph nodes.
- M describes whether the cancer has spread to another part of the body, such as the liver or lungs (known as metastatic or secondary cancer).
Doctors put numbers after the T, N, and M that give more details about the size and spread of the cancer.
Information from the TNM system and the grade of the cancer can be used to give a number stage. The number staging system is different depending on where the GIST has started.
Generally, GISTs are divided into four stages:
- Stage 1 – the cancer is small, low grade and has not spread.
- Stage 2 and 3 – the cancer is bigger, may be either low or high grade and has not started to spread.
- Stage 4 – the cancer has started to spread into nearby lymph nodes or other parts of the body.
Your doctor or specialist nurse can give you information about the grade and stage of the cancer.
The treatment for a GIST depends on a number of things, including:
- your general health
- where the cancer started
- the size of the tumour
- the mitotic rate of the tumour.
The results of your tests help your doctors decide on the best treatment for you. They will then discuss this with you.
The main treatments for GIST are:
You may be offered some treatments as part of a clinical trial.
Chemotherapy and radiotherapy do not work well for this type of cancer, so they are not used.
Because GISTs are rare cancers, you should be referred to a specialist unit for treatment. This may mean you need to travel further to have your treatment.
Most smaller GISTs are treated with surgery. If there is a high risk that the GIST could come back after surgery, you may also have targeted therapy to reduce the risk (adjuvant treatment).
If the GIST is small (less than 2cm) and is not causing any symptoms
Your doctor may suggest monitoring the tumour with regular endoscopies. Some small GISTS grow very slowly and may not need treatment. If the tumour starts to grow, you will be offered surgery. But if it is not growing, you will not need any treatment.
If the GIST is bigger, or is harder to remove because of where it has developed
If surgery is not possible, or if the cancer has spread to other parts of the body
If GIST comes back
If a cancer comes back after its first treatment, it is called recurrent cancer. It may come back:
- in the tissues where it first started, called a local recurrence
- in another part of the body, called a metastasis or distant recurrence.
If the GIST comes back after treatment, it is usually treated with targeted therapy. Surgery may also be an option for small, single recurrences.
Your doctor or specialist nurse will discuss your treatment options with you.
Surgery for GIST
The surgeon removes the tumour, along with some surrounding healthy tissue. If the tumour has started to grow into other organs close by, the surgeon may also remove these.
The aim is to make sure they take away all the GIST cells. Surgery may also be used to treat GISTs that come back after treatment.
If the GIST is in the small bowel, you may have an operation to remove part of the small bowel. This does not usually have any long-lasting side effects.
If you have a GIST in the stomach, you may need to have part, or most, of the stomach removed. This may mean making changes to your diet, particularly the size and frequency of your meals. Specialist dietitians can give you advice and support.
Your surgeon will tell you about any possible effects of the surgery. These depend on the size of the tumour and where it is in the body.
We have more general information about having surgery.
Targeted therapies for GIST
Targeted therapies are drugs that interfere with the way that cancer cells grow. Growth inhibitors are a type of targeted therapy. They work by blocking signals in the cancer cells that make them grow and divide.
In more than 8 out of 10 of people with a GIST (about 85%), the tumour cells have a change (mutation) in a protein called KIT. This change means the GIST cells constantly get signals telling them to grow and multiply.
Treatment with growth inhibitors can block these signals. This may shrink the cancer or stop it growing. There are 3 growth inhibitors that can be used to treat a GIST. These are:
We have more about treating GIST with these drugs in our information about targeted therapy for soft tissue sarcomas.
Everyone has their own way of dealing with illness and the different emotions they experience. You may find it helpful to talk things over with family and friends or your doctor or nurse.
Macmillan can offer emotional, practical and financial help and support. You can call us on 0808 808 00 00.