Gastrointestinal Stromal Tumors (GIST) Overview

Cancer occurs when normal cells become abnormal and quickly grow.  These cells can then form a growth of tissue called a tumor.  A tumor can be noncancerous (benign) or cancerous (malignant).  If cancerous, the tumor cells can spread to other parts of the body (metastasize). 

Gastrointestinal stromal tumor, also known as GIST, is a rare type of cancer.  It can develop anywhere along the digestive or gastrointestinal (GI) tract.  The digestive tract includes the esophagus, stomach, gallbladder, liver, small intestine, colon, rectum and lining of the gut.  GIST cancer develops in cells found in walls of the digestive tract.  These cells are known as the interstitial cells of Cajal.  These cells produce a protein called c-Kit and are sometimes called the “pacemaker” cells of the gut.  They help to make sure that food continues to moves through the gastrointestinal tract.  Because GISTs come from the cells in the mesenchymal tissue, it is categorized as a soft-tissue sarcoma. 

GISTs usually start in the stomach.  But they can also start in the small intestine, omentum (a large fatty structure which literally hangs off the middle of your colon and drapes over the intestines inside the abdomen) or lining of the abdomen (mesentery), colon, and esophagus.  GISTs often start in the second layer of the bowel wall.  Here they can either grow inward towards the part of the bowel where food passes or outward.  If a GIST spreads to other parts of the body, it will usually metastasize to the liver and abdominal cavity.  GISTs usually do not spread to the lymph nodes.     

A risk factor is anything that increases a person’s chance of developing a specific cancer. There are no known risk factors for GIST.  The majority of GISTs develop for no reason at all. 

People who have GIST may have different signs and symptoms or none at all.  The most common symptom caused by GIST is gastrointestinal (GI) bleeding.  People with GI bleeds may vomit blood, have black tarry or tar-like stools or have bloody stools.  The symptoms depend on where the GIST tumor is located.  GI bleeding can also cause anemia (low red blood cell count) which can leave a person feeling fatigued or tired.  If the GIST is large, it can cause a blockage in intestine.  This intestinal blockage may cause the patient to have nausea, vomiting, really bad abdominal pain, and constipation.  Signs of GIST can be minor and overlooked by the patient.  It is important to pay attention to any changes in your body.  You should speak to your physician if you experience any of these signs or symptoms. 

Treatment of gastrointestinal stromal tumors depends on the size of the tumor and whether cancer cells have spread to other parts of the body. If caught at an early stage, meaning the tumor is localized and has not spread to distant or nearby organs, the GIST may be treated with surgery alone. Surgery is the removal of the tumor and surrounding tissue during an operation. If the GIST is too large or if it has spread to other organs of the body, surgery alone will not be able to remove all of the cancer.  In these cases, the patient may be able to receive a targeted therapy called imatinib prior to surgery. Targeted therapy is a treatment that targets the cancer's specific genes or proteins that help cancer cells grow and survive. Targeted therapy stops the growth and spread of cancer cells while causing little damage to normal cells.  Because it targets only cancer cells, targeted therapy usually has fewer side effects than other cancer therapies. The goal of being treated with imatinib prior to surgery is to shrink the tumor to a smaller size. A smaller sized tumor will hopefully make the surgical removal safe and easier for the patient. Patients who take imatinib prior to surgery will usually have to take it for an extended period of time after surgery. Unlike other tumors, traditional chemotherapy agents are not effective in the treatment of GIST and are usually not used. Radiation therapy, which is the use of high-energy x-rays or other particle to kill cancer cells, is not often used in the treatment of GIST. This is because it is currently not known whether the GIST is affected by or responds to radiation therapy. Patients may also want to consider participation on a clinical trial.  A clinical trial is meant to obtain information on new treatments for patients with cancer. It is important to discuss all of your options with your medical oncologist and treatment care team and together decide which treatment is best for you.