GIST stands for GastroIntestinal Stromal Tumour. A GIST occurs when special cells within the wall of the gastrointestinal (GI) tract change so that they grow more than they should. It is a specific type of tumour that comes under the umbrella medical term of 'sarcoma'. This can affect any part of the GI tract, from the gullet (or oesophagus) to the rectum. The most common site for these tumours is the stomach. Most often, they are picked up when tests are performed for symptoms caused by something else, such as an endoscopy for indigestion, although they can also cause a variety of symptoms, the most common of which are explained below. Compared to other types of oesophageal or gastric tumour, they have a much lower risk of spreading.

Figure 1. GIST within the stomach as seen at upper GI endoscopy. Credit: Samir Grover, 2004.

Bleeding and anaemia

Sometimes GISTs can develop an ulcer on their surface and bleed. Sometimes this bleeding is so slow that it cannot be seen. It may, however, cause enough blood loss that a person becomes anaemic. This may cause a feeling of tiredness and lethargy, and a person may get out of breath more easily than normal. In other patients, they can cause more noticeable bleeding which may resulting in vomiting up blood, or a patient's stool (or faeces) may turn very dark, smelly and become sticky like tar.

Bowel obstruction

Depending upon the size or position of the tumour, a GIST can cause a blockage to the flow of food and drink through the guts. This is more common when a GIST is either big or is located at a narrow point in the gut. If this causes a blockage, a person may develop crampy pain, bloating, nausea and vomiting, and ultimately they may stop opening their bowels. This is a relatively uncommon problem with GISTs.

Bloating or swelling

Sometimes a GIST may be diagnosed once it has grown very large when it causes bloating or swelling of the abdomen because of the amount of space it occupies inside the tummy.

A number of different tests can be performed to assess people who might have a GIST, to make the diagnosis and to make further assessments to plan treatment. Our cancer care is provided as part of a regional network. Patients may therefore have different tests in different hospitals. As far as possible, we will minimise the number of trips and travel distances required. However, we also need to make sure we gather the correct information from the different tests available to make the right treatment decision for each patient.

Upper GI endoscopy

One of the most common way GISTs are diagnosed is when a person is having an upper GI endoscopy (often referred to as an OGD) for other symptoms. This is a common procedure involving the insertion of a thin tube with a camera on the end through the mouth into the oesophagus, stomach and first bit of the small bowel called the duodenum. This test is important to look for a range of problems such as acid damage or an ulcer. It is a routine procedure, but as with any test there are benefits and risks, even though the risks are low. More information on this procedure, its benefits and risks are available  here.

Computed Tomography (CT)

Another common way GISTs are diagnosed is when a person has a CT scan. A GIST may be detected when someone is having a CT scan for other symptoms that are not related to the GIST. A CT scan is also an important part of assessing a GIST to check the size of the tumour and look for any evidence of spread. Having a CT scan involves lying down on a narrow bed which moves through an open ring, like a big doughnut. The scan itself usually takes a few minutes. It involves exposure to x-rays, a form of ionising radiation. Doctors always minimise the amount of radiation to which patients are exposed. For people with a GIST, the benefits of this test and the information it provides to plan treatment outweigh its risks.

Endoscopic Ultrasound (EUS)

Sometimes, patients require a more invasive form of scan called an Endocsopic UltraSound or EUS. This procedure is performed under sedation in the endoscopy department. A telescope with a very small ultrasound probe on the end is passed through the mouth into the oesophagus, stomach and /or duodenum to get close up pictures of the GIST. In addition to having a very close look at the GIST, this procedure can be also be used to take small samples (or biopsies) of the tumour to confirm that it is a GIST. It can take up to 2 weeks for any samples to be examined under a microscope and receive the result. As EUS is an invasive test, there are small risks associated with the procedure, which the team will explain to you if you are having this test.

Other tests

Occasionally, other tests are required. These may be required to look at specific areas identified by the above tests. For example, the scans may detect an abnormal area on the lower bowel. This may then mean that a telescope examination of the lower bowel is required to know exactly what is going on at the abnormal area. In addition, tests may be required to help assess fitness for treatments. These include tests to examine how well the heart or lungs are working, to know if a person is fit enough to have major surgery. Your doctor will explain any additional tests and why they may be needed.

After having tests to diagnose and assess a GIST, your doctor will discuss your treatment options with you. Treatment options are determined at a weekly meeting of specialists where all the test results are discussed. A lot of different doctors are involved in making these decisions, including surgeons, oncologists (cancer specialists), radiologists (imaging specialists), histopathologists (experts in tissue analysis) and cancer nurse specialists. This meeting is called the 'Multi-Disciplinary Team' (MDT) meeting. This means that the right decisions can be made with you based on the specific details of you and your test results.

The main factors determining your treatment include the site of the GIST, its size, your fitness for treatment, and whether there is any evidence of spread. In general, the treatment options available are explained below.

Watchful waiting

Small GISTs may not require any treatment. In this case, the team may recommend that a further scan is performed after a period of time (such as one year) has elapsed to see if it is growing or not. Some GISTs will either not grow, or only grow very slowly, and may never need any form of treatment.

Surgery

Once a GIST reaches a certain size, the team may recommend surgery. Many GISTs that affect the stomach can be treated by removing a limited portion of the stomach, often by key-hole surgery, although a bigger cut may be needed to remove the tumour from inside the abdomen. However, bigger GISTs, and those affecting certain parts of the stomach, can be more difficult to remove, requiring more major surgery, or open surgery. As the nature of the required surgery is variable, the risks and consequences are also quite variable. Your doctor will tell you more about your particular tumour, and what will be involved if surgery is recommended as well as the associated risks.

Chemotherapy

In some cases, the team may recommend treatment with specific medication (imatinib, or a similar drug) which acts directly on the GIST. This is a very focused treatment, and therefore has fewer side effects than more common forms of chemotherapy. Your doctor can explain this treatment in more detail.

Here are some useful links to other sources of information and support for patients who have a GIST.

Cancer Research UK:

https://www.cancerresearchuk.org/about-cancer/soft-tissue-sarcoma/types/gastrointestinal-stromal-tumour

Macmillan:

https://www.macmillan.org.uk/cancer-information-and-support/soft-tissue-sarcoma/gastrointestinal-stromal-tumour

GIST Support UK:

https://www.gistsupportuk.com/

Sarcoma UK:

https://sarcoma.org.uk/sarcoma-types/gastrointestinal-stromal-tumours-gist