Gastrointestinal Stromal Tumor (GIST)
Gastrointestinal stromal tumors (GISTs) are relatively rare tumors of the GI tract. They start in special cells found in the wall of the GI tract, called the interstitial cells of Cajal (ICCs), or in very early cells that can develop into ICCs. These cells are sometimes called the "pacemakers" of the GI tract because they send signals to the muscles in the digestive system after eating, telling them to contract to move food and liquid through the GI tract. Although these tumors can start anywhere in the GI tract, they occur most often in the stomach (50% to 70%) or the small intestine (20% to 30%). The rest are found in the esophagus, large intestine (colon and rectum), and anus.
While most GISTs are cancerous, some GISTs are benign -- they don't grow into other areas or spread to other parts of the body.
The exact number of people diagnosed with this tumor each year is not known. Based on various studies, estimates for the total number of GIST cases each year in the United States have ranged from about 4,500 to about 6,000. Of these, about 1,500 have already spread to distant sites (metastasized) when they are initially found.
Most people diagnosed with GIST are older than 50, but these tumors can occur in people of any age. They are slightly more common in men. African Americans are more likely to develop GISTs than whites.
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Medical treatment: targeted therapy
A drug called imatinib (Gleevec), initially developed by OHSU Knight Cancer Institute Director Brian Druker, M.D., is very helpful for many GIST patients. Overall, in about 2 out of 3 patients treated, the tumors shrink by at least half. In a small number of patients, there is only mild shrinkage or at least no further growth. In about 15% of patients, the drug doesn't help and the cancer continues growing.
Researchers at the OHSU Knight Cancer Institute, such as Michael Heinrich, M.D., are working to determine how to tailor therapy based on the genetic makeup of GISTs. Read more
While Gleevac doesn’t seem to cure advanced GISTs, it can help people with them live longer. Often, the drug stops working within a few years and then the cancer starts growing again. Raising the dose of imatinib may help stop the growth of the cancer for some time, but the higher dose has more side effects. Although the vast majority of GISTs respond well to Gleevec treatment, tumors can become resistant and regrow over time. To combat this problem, a second drug, Sutent (sunitinib), was tested in clinical studies and shown to be active in treating Gleevec-resistant GIST. Like Gleevec, Sutent targets specific enzymes. However, unlike Gleevec, Sutent can also block blood vessel formation in GISTs.
Surgery is usually the main treatment for a small gastrointestinal tumor (GIST) that hasn't spread to other parts of the body. If the tumor is very small, it often can be removed with a small area of normal tissue around it. Unlike many other cancers, removing the nearby lymph nodes is usually not needed, because GIST does not often spread to the lymph nodes. The goal of the surgery is to completely remove all of the cancer.
If the tumor is large or growing into other organs, the surgeon may still try to remove it by removing portions of other organs (such as sections of the intestines). Even if the tumor is large and has spread into other organs, this may help patients live longer. It can also reduce the chances that the cancer will block (obstruct) the digestive tract later on. The surgeon may also remove GISTs that have spread elsewhere in the abdomen, such as the liver.
Led by internationally renowned medical oncologist, Dr. Michael Heinrich, our GIST cancer team is a leader in cancer care and research and treats more GIST cancers than any other hospital in Oregon.