GastroIntestinal Stromal Tumour or GIST is not one of the common digestive tract cancers such as stomach cancer. Most GI cancers are carcinomas arising from skin-like linings of the GI tract, but GIST is a sarcoma. Sarcomas arise in the connective, or supportive, tissue (including fat, muscle, blood vessels, nerves, bone, cartilage). GISTs develop from the nerve networks between the muscular wall layers of digestive organs.
Because GISTs arise from the walls (not the interior) of the digestive tract and usually grow outward into the abdominal cavity, they may not cause any symptoms until they have become quite large. Patients may have vague digestive discomfort or may notice a mass in the abdomen. Often the first symptom is anaemia from slow tumour bleeding, or possibly abdominal pain from a rupture or tarry stools from a haemorrhage. GISTs are frequently discovered incidentally due to CT, MRI or ultrasound scans being performed for another reason, or to investigate abdominal discomfort.
Causes of GIST
There are no identified risk factors for GISTs. Only about 20 families worldwide are known to have inherited predispositions to develop GIST. The cause of most GISTs is a mutation in a gene that results in a change to a growth factor receptor protein on the surface of cells. Most GISTs exhibit mutations in the KIT gene, but a minority have mutations in the PDGFRA gene. When either of these genes is mutated, the corresponding receptor proteins signal abnormally without stimulation by their growth factors. This abnormal signalling results in uncontrolled growth – a tumour. 10-15% of GISTs are called “wildtype” because they lack any of the identified mutations. A handful of GISTs show a mutation in the BRAF gene.
50-70% of GISTs arise in the stomach, and 20-30% in the small intestine, with small percentages in other abdominal locations. About half of all patients with newly-diagnosed GIST already have metastases.
If possible, GIST tumours are removed surgically with clear margins uncontaminated by tumour tissue, and surgery may be curative for smaller tumours. For many patients, however, surgery alone is insufficient for the treatment of GIST. Risk of recurrence or metastasis after removal of primary GIST can be estimated from prognostic categories. Effective targeted drug therapies for GIST have been developed that act specifically on the cell surface growth factor receptor proteins mentioned above. Targeted treatments have fewer side effects than conventional chemotherapies.
A drug called imatinib (trade name Glivec) is generally used as first line of treatment. This is often used before surgery to try to make the surgery more manageable (called neo-adjuvant treatment), after surgery to try to prevent a recurrence (called adjuvant therapy in the absence of detectable disease), or as treatment for metastatic disease or an unresectable tumour.
If the disease progresses while the patient is taking imatinib, then it is possible to take sunitinib, and subsequently other drugs are available.
Learn as much as you can about GIST – there is plenty of material available on the internet – from the large international patient advocate groups or from a group in your country. You can contact one of these groups to find a group nearer to home, and possibly in your mother tongue. These groups usually have email groups for their members where you can ask questions, get advice and share experiences, and they may arrange meetings where you can meet others and learn more.
Many GIST patients choose to travel to expert sarcoma centres for consultations or for regular care. You may be able to find good care locally, but if you choose this course you will need to take more responsibility to participate in treatment decisions based on the realization that you have a rare disease.
You are not alone with this disease, as rare and unusual at it may seem – and hearing about the many who are living full and happy lives long after initial diagnosis is both heart warming and heartening!
For further reading please visit
http://www.daslebenshaus.org (German website)