Gastrointestinal stromal tumour (GIST)

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)
• being sick (vomiting)
• blood in your poo (stools) or vomit
• anaemia (low level of red blood cells)
• a painless lump in the tummy
• feeling tired and weak (fatigue)
• a high temperature (fever) and sweating at night
• losing weight for no obvious reason.

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. They are diagnosed with GIST by chance when having a test or scan for another reason.

You usually start by seeing your GP, who will examine you. You may also have blood tests to check your general health and the number of cells in your blood (blood count).

If your GP is not sure what the problem is, or thinks your symptoms could be caused by cancer, they refer you to a specialist doctor.

At the hospital, the specialist doctor will ask you about your symptoms and your general health. They will examine you and arrange some of the following tests.

Tests for GIST

There are different tests that might be used to help diagnose GIST. Our cancer support specialists or your specialist doctor or nurse can give you information about any tests we do not explain here.

Testing the cancer cells for genetic changes

The laboratory will also test cells from the biopsy or surgery to look for genetic changes in the tumour cells. These changes are called mutations. They can tell doctors whether treatment with targeted therapy drugs is likely to be helpful.

A team of specialists meets to discuss the best possible treatment plan for you. This is called a multidisciplinary team (MDT). Treatment of a GIST depends on different things, including:

• where the GIST is in the body
• the size of the tumour
• the grade of the GIST (its mitotic rate)
• your general health
• if the GIST cells have certain genetic changes.

Your doctor and nurse will talk to you about the best treatment for you. They can talk to you about things to think about when making treatment decisions.

The main treatments for a GIST are surgery and targeted therapy drugs. Chemotherapy is not a helpful treatment for GISTs. Radiotherapy is rarely used.

Risk groups

After surgery to remove a GIST, doctors decide whether it is low-risk or high-risk. They look at where the GIST started, its size and mitotic rate. A tumour that bursts during surgery is also high-risk.

Because high-risk GISTs are more likely to come back your doctor will usually advise treatment with targeted therapy after surgery.

Monitoring

Some small GISTs grow very slowly and may not need treatment. If the GIST is less than 2cm and is not causing symptoms, your doctor might suggest monitoring the tumour. You will have regular endoscopies or scans. If the tumour starts to grow, you can then have surgery.

Targeted therapy drugs called tyrosine kinase inhibitors (TKIs) are used to treat GIST. In more than 8 out of 10 GISTs (about 85%), the tumour cells have a change in a protein called KIT. This change (called a mutation) means the GIST cells constantly get signals telling them to grow and multiply. TKIs block these signals. Tests on the cancer cells are done first to find out how helpful these drugs are likely to be. Imatinib is a TKI drug given:

• before surgery, to reduce the size of the GIST and make surgery more effective
• after surgery, for 3 years, to reduce the risk of GIST coming back (called adjuvant therapy)
• to treat a GIST that cannot be operated on or has spread to other parts of the body.

If imatinib stops working or is causing difficult side effects, you may be given sunitinib (Sutent^®) or regorafenib (Stivarga^®).

If the GIST is bigger than 2cm, you may have surgery to remove it. You may have targeted therapy before surgery to shrink the tumour. If the GIST is found to be high-risk, you usually have targeted therapy after surgery.

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. 

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. 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 the GIST is in the stomach, you may have part or most of the stomach removed. A specialist dietitian can give you advice and support.

Surgery may also be used to treat GISTs that come back after treatment. We have more information about surgery for soft tissue sarcoma.

You may be offered some treatments as part of a clinical trial.

If a GIST comes back after treatment it may come back where it first started. This is called a local recurrence. Or it may come back in another part of the body which is called secondary or metastatic cancer.

GIST that comes back is usually treated with targeted therapy. Surgery may also be an option if there is only 1 small new GIST. Your doctor or specialist nurse will talk to you about your treatment options

If GIST comes back in the liver it is called secondary liver cancer. The following treatments may be used:

• radiofrequency ablation (RFA) which uses heat to destroy the cancer cells
• cryotherapy which uses cold to destroy the cancer cells.

These are called tumour ablation treatments. 

Some people might have a type of radiotherapy called stereotactic ablative radiotherapy (SABR).

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