Gastrointestinal stromal tumors (GISTs) are soft tissue sarcomas that can be located in any part of the digestive system. Their most common sites are the stomach and small intestine.
GISTs start in specialized nerve cells located in the walls of your digestive system. These cells are part of the autonomic nervous system. A specific change in the DNA of one of these cells, which control such digestive processes as movement of food through the intestines, gives rise to a GIST.
Small GISTs may cause no symptoms, and they may grow so slowly that they have no serious effects. People with larger GISTs usually seek medical attention when they vomit blood or pass blood in their stool due to rapid bleeding from the tumor.
Other possible GIST symptoms include:
GISTs can develop in people of all ages, but they are most common between age 50 and 70, and they almost never occur before age 40. In rare cases, an inherited genetic change (mutation) causes GISTs.
After asking questions about your symptoms and medical history, your doctor will examine you carefully, checking for a growth in your abdomen. If signs and symptoms suggest that you may have a GIST, tests to locate it and then determine its likelihood of spreading (metastasizing) to other organs will follow. These tests may include:
Fine-needle aspiration biopsy. A small sample of tissue from the tumor is necessary for a definite GIST diagnosis. The preferred method for taking a biopsy sample is endoscopic ultrasound with fine-needle aspiration. This procedure is the same as an EUS, but with a thin, hollow needle on the tip of the endoscope. The needle is used to remove small amounts of tissue for laboratory analysis.
Sometimes these tests aren't possible, or their results are inconclusive, so a suspected GIST can't be located without surgery. Tissue analysis then takes place after the tumor is removed.
Small, asymptomatic GISTs found in the course of tests for another condition may be approached with watchful waiting in carefully selected cases.
Usually, large or symptomatic GISTs are surgically removed unless they are too large or they involve too many organs and tissues for surgery. Resection is also delayed or avoided in people whose general health makes any surgery too risky to undertake, as well as in those likely to have metastatic GISTs.
It's often possible to resect GISTs using minimally invasive surgery, which involves inserting a viewing tube (laparoscope) and surgical instruments through small incisions in the abdomen.
Targeted drug treatments focus on specific abnormalities present within cancer cells. By blocking these abnormalities, targeted drug treatments can cause cancer cells to die. For GISTs, the target of these drugs is an enzyme called tyrosine kinase that helps cancer cells grow.
Imatinib (Gleevec) is the first line targeted therapy used to prevent GIST recurrence after surgery. The drug is also used to shrink the tumor before surgery, in situations where surgery isn't possible, as well as for controlling recurrent GIST. Treatment generally continues as long as the drug is effective.
Other drugs that target tyrosine kinase might be recommended if your GIST doesn't respond to or becomes resistant to imatinib over time. Targeted drug therapy is an active area of cancer research and new medications are likely to be available in the future.
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