What is GIST? 

GIST stands for Gastrointestinal Stromal Tumour. GIST is a very rare cancer that affects the digestive tract or nearby structures within the abdomen. They are a type of sarcoma. Sarcomas are cancers that grow from cells of the body’s connective or supportive tissues such as bone, cartilage, tendons, nerves, fat, muscle, synovial tissue (tissue around joints), or blood vessels. About 1% of cancers in adults are sarcomas and GIST is one of approximately 50 types of sarcoma. GIST may occur anywhere along the gastrointestinal tract; however, the most frequent site for them is the stomach (approximately 55%), then the duodenum and small intestine (approximately 30%), the esophagus (approximately 5%), the rectum (approximately 5%), the colon (approximately 2%), and then other locations. Gastrointestinal stromal tumours are quite rare. There are about 1.4 million new cases of cancer every year in the United States and about 15 000 of these are sarcomas. Some studies have shown that about 3000-4000 GIST cases are seen per year in the United States. No statistics could be found for Canada. Many doctors and other medical professionals go through their career without ever seeing a single GIST. The median age at which sporadic GIST is found is about 60 years old.

 

How is it Caused? 

There are no known environmental or behavioural risk factors contributing to GIST. The apparent cause of GISTs are random genetic mutations. The majority of GISTs show identified mutations in cell surface proteins called tyrosine kinase receptors. Most GISTs show mutations in a gene that produces a growth factor receptor called KIT. A few GISTs show mutations in the gene for a closely related receptor for platelet derived growth factor receptor alpha (PDGFR a or PDGFRA). A few GISTs are normal or “wildtype” for both these genes and the causal mutations or these GISTs have not been identified. The vast majority of GISTs are sporadic which means that the mutations are random occurrences affecting a single individual. There are also rare examples of GIST running in families due to an inheritable germline mutation. 

 

Symptoms 

Many people who have GIST (usually those with smaller tumours) do not show any symptoms. Larger tumours can cause symptoms that are related to the increased mass being accommodated in the abdominal cavity. Symptoms may include digestive discomfort, sensations of abdominal fullness, abdominal pain, vomiting, or diarrhea. With larger tumours, they may be detectable as a mass when feeling the abdomen or visually as an enlargement of the abdomen. Although many symptoms are possible, they are mostly indistinct and just related to the additional mass that is present in the abdomen. As a result, many GISTs are found by accident through medical imaging tests for other purposes or through surgery for other conditions. 

 

Treatment 

Surgery is the first and foremost treatment for GIST wherever resection is possible. Although complete removal of the tumour is potentially curative there is always a chance of recurrence. If recurrence does happen, it is normally within the first two years after surgery to remove a primary tumour. However, there are cases where it as re-occurred 10-20 years later. A new drug called Glivec (imatinib mesylate) is the first effective treatment for GIST. It is the first marketed “molecularly targeted therapy” for cancer meaning that the drug affects only those cells that express highly specific targets. This is in contrast to conventional cancer chemotherapies that affect all fast growing cells in the body. Glivec targets two growth factor receptors - KIT and PDGFRA. This drug is also used for chronic myelogenous leukemia.

 

Note: This has just been an overview of this condition. For more information please contact your doctor.