What is GIST?
A gastrointestinal stromal tumour (GIST) is a type of growth (tumour) that occurs in the gastrointestinal (digestive) tract. It arises from the wall layer of the GIT in cells called interstitial cells of Cajal. GISTs occur in any part of the digestive tract from the oesophagus to the rectum but they are most common in the stomach (60%) and small intestine (30%). GISTs may be malignant (cancer) or benign (not cancer).
How different it is from the usual stomach cancer?
Usual stomach cancer (adenocarcinoma) arises from the lining layer of the stomach while GISTs arise from the wall of the stomach. Click here to read more about stomach cancer.
What are the risk factors for GIST?
The majority of GISTs occur without a known reason. Rarely patients with genetic syndromes, such as neurofibromatosis, have an increased risk.
What are the symptoms of GIST?
GISTs tend not to cause symptoms till they are big. The symptoms depend on the size and location of the tumour:
1. Pain in the abdomen
2. Abdominal mass
3. Nausea and vomiting
4. Vomiting of blood or passage of blood in stool
5. Anaemia (low blood count) causing fatigue
6. Weight loss
What are the tests for GIST?
Tests are done depending on the symptoms and location. Once the diagnosis is made or suspected further tests are performed to assess the extent of the disease (staging).
1. Endoscopy: gastroscopy & colonoscopy
2. CT scan
3. MRI scan
4. Endoscopic ultrasound
5. PET CT scan
6. Biopsy: A biopsy is the removal of small amount of tissue for examination under microscope. Other tests can suggest the diagnosis but only a biopsy can make the diagnosis. A biopsy of GIST is not always possible and sometimes, surgery is performed without a definitive diagnosis until after surgery.
What are the treatment options for GIST?
The treatment options depend on many factors including the type, location, stage, symptoms, and the patient's overall health and preferences.
Small GIST are very common and may not require treatment. Close monitoring may be appropriate.
Removal of the tumour and surrounding tissue is the standard of care for patients with localized disease. Surgery may be done via open technique or laparoscopic (key-hole) technique. GIST in the stomach are treated with distal, subtotal or total gastrectomy depending on the size and location.
Targeted therapy is the use of certain drugs that attack specific tumour cells without affecting normal cells.
Tyrosine kinase inhibitors such as Imatinib (Gleevec or Glevic) and Sunitinb block signals needed for GISTs to grow. They cause the tumour to shrink. These drugs are one of the newest break throughs in the treatment of cancer. They are used in different ways:
1. To shrink a very large tumour to allow it to be removed by surgery later on.
2. To reduce the chance of an aggressive type of tumour from coming back after surgery.
3. To control tumour that has spread to other organs or that has grown beyond surgery.
4. To treat recurrent disease.
GISTs do not respond well to radiation therapy but radiation may be used to palliate symptoms such as reduce pain or bleeding.
GISTs do not respond to chemotherapy and therefore it is not used.