A gastrointestinal stromal tumour (GIST) is a rare type of sarcoma (cancer arising from bones or soft tissues) that forms in lining of the gastrointestinal tract. More specifically, they develop in interstitial cells of Cajal (ICC), which play a critical role in the intestinal contractions required for digestion. The gastrointestinal tract is primarily responsible for food digestion and nutrient uptake, and is made up of organs such as the stomach, small intestine, and large intestine (colon).
GISTs in adults are slightly more common in males and are generally diagnosed in people between the ages of 50 and 70. They are most commonly found in either the stomach, or the small intestine. While this disease has higher incidence in adults, children and teenagers are also able to develop this disease. In paediatric cases, GISTs are more common in girls and tends to be diagnosed in the teen years. In children and teenagers, GISTs are usually found in the stomach.
Treatment
If a GIST is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumour) indicates the size and depth of the tumour.
- N (nodes) indicates whether the cancer has spread to nearby lymph nodes.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including age, location, stage of disease and overall health.
Treatment of Childhood GIST
Due to the rarity of GIST in childhood, there are fewer treatment options than adults with GIST. Treatment options for childhood GIST may include:
- Surgery, potentially including:
- Keyhole surgery (laparoscopy).
- Gastrectomy (partial/total removal of the stomach).
- Intestine resection (partial/total removal of intestine).
- Abdominoperineal resection (partial/total removal of the anus, rectum and sigmoid colon).
- Pancreaticoduodenectomy, also known as a Whipple procedure (removal of portions of the pancreas, small intestine/duodenum, gall bladder and/or stomach).
- Targeted therapies.
- Clinical trials.
- Palliative care.
Treatment of GIST in adults
Adults with GIST have more treatment options that children with this disease. However, like childhood GIST, chemotherapy and radiation therapy are not often used to treat this type of cancer.
Treatment options for GISTs in adults may include:
- Surgery, potentially including:
- Keyhole surgery (laparoscopy).
- Gastrectomy (partial/total removal of the stomach).
- Intestine resection (partial/total removal of intestine).
- Abdominoperineal resection (partial/total removal of the anus, rectum and sigmoid colon).
- Pancreaticoduodenectomy, also known as a Whipple procedure (removal of portions of the pancreas, small intestine/duodenum, gall bladder and/or stomach).
- Targeted therapies.
- Watch and wait.
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Some of the information regarding treatment was obtained from the Gastrointestinal Stromal Tumors Treatment (Adult) (PDQ) and the Childhood Gastrointestinal Stromal Tumours Treatment (PDQ) pages published by the National Cancer Institute.
Risk factors
The risk factors for developing GIST, as an adult or a child, include having genetic conditions such as:
Certain genetic mutations have also been linked to the development of GIST. The genes commonly affected include:
- Tyrosine c-KIT.
- PDGFRA (platelet derived growth factor receptor alpha) receptors.
Some fewer common genes affected can include:
- Succinate Dehydrogenase (SDH).
- Neurofibromatosis gene 1 (NF1).
- BRAF V600
- Rat sarcoma (RAS).
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Early symptoms
GIST may appear asymptomatic in the early stages. Adults and children with GIST may experience some of the following symptoms:
- Blood in stool and/or vomit.
- Abdominal pain and/or mass.
- Bloating.
- Fatigue.
- Difficulties/pain when swallowing.
- Unexplainable weight loss/loss of appetite.\
- Nausea and/or vomiting.
- Anaemia (low levels of red blood cells).
- Blocked intestines, which carry its own set of symptoms:
- Abdominal cramping and/or swelling
- Nausea and/or vomiting.
- Diarrhoea.
- Constipation.
Not everyone with the symptoms above will have cancer, but see your GP if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have a GIST, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment.
Genetic testing
In addition to guiding treatment, genetic testing can be used to help diagnose certain conditions. GIST has been linked to mutations in the KIT (receptor tyrosine kinase gene), PDGFA (platelet-derived growth factor A gene) and SDH (succinate dehydrogenase gene) genes, which all change specific protein functions. These changes can lead to cell abnormalities and, in extreme cases, cancer. Your doctor may perform genetic testing to better understand your condition.
Physical examination
Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.
Imaging & blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Endoscopy & biopsy
An endoscopy is a surgical procedure that involves inserting a long, flexible tube with a light and small camera through oesophagus, stomach and the first part of the small intestine. You will be given a sedative or anaesthetic throughout the procedure. You will be asked to fast for several hours prior to the procedure. An endoscopy is often done as a day surgery. Your doctor will discuss the risks and any possible complications prior to the procedure.
Throughout the procedure, your doctor may also perform an endoscopic ultrasound to guide the needle during a biopsy, or to check for signs of cancer metastasis.
If any abnormalities are observed, your doctor will remove a small tissue sample for analysis.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage GISTs have a better prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.