Gastrointestinal Stromal Tumor (GIST)

What is a GIST?

GIST is a rare cancer of the gastrointestinal (GI) tract, also called the digestive tract. A tumor can happen anywhere in your GI tract, from the esophagus to the anus. GIST starts in cells called the interstitial cells of Cajal. These cells are part of the nervous system. They send signals to the muscles of your GI tract. This helps your GI tract move food and liquid through it.

What causes GIST?

Researchers are still learning what causes GIST. In most cases, a gene causes an enzyme called KIT to be produced. KIT tells cells in the gut to keep growing and multiplying. This causes a tumor to grow. In rare cases, a different protein (called PDGFRA) causes cells to grow too much and causes a tumor. GIST may run in families who have a genetic syndrome called neurofibromatosis type 1. Carney-Stratakis syndrome is another inherited condition that puts people at a higher risk of GIST.

Symptoms of GIST

You may not have any symptoms if you have early stage GIST. In later stages, symptoms may include:

• Discomfort or pain in the stomach

• Vomiting

• Blood in stools or vomit

• Tiredness from low levels of red blood cells (anemia)

• Feeling full after eating only a small amount

• Loss of appetite

• Weight loss

Diagnosing GIST

Your healthcare provider will ask about your medical history and your symptoms. He or she will give you a physical exam. You may have imaging tests, such as:

• Endoscopy. A flexible tube is sent down your throat. The tube has a small light and video camera. This lets your healthcare provider look at the lining of your esophagus, stomach, and upper small intestine.

• CT scan. This is a test that uses a series of X-rays and a computer to create images of the inside of the body.

• MRI. This test uses large magnets and a computer to create images inside of the body.

• Biopsy. Small pieces of tissue are taken from the tumor. They are looked at with a microscope in a lab. A biopsy may be done during endoscopy. Or it may be done with a thin needle. Or the tissue may be removed during surgery. The sample will be checked for the KIT enzyme and examined to see if it contains cancer cells.

Treatment for GIST

GIST can be treated in several ways. GIST grows differently in each person. The type of treatment that is best for you depends on where the tumor is, how big it is, and whether cells from the tumor have spread to other parts of your body. This is called metastasis. The most common places for GIST cells to spread are the liver and the lining of the stomach (peritoneal cavity).

Treatment may start with surgery. This is done to remove the tumor.

You may also have targeted therapy. Targeted therapy is the use of medicine that targets the parts of cancer cells that make them unlike normal cells. The medicines commonly used include:

• Imatinib. This is often the first drug used for GIST. It can be given before surgery to try to shrink the tumor, or after surgery to help lower the chance of the cancer coming back. It may not cure advanced GIST, but it can help people live longer and feel better. The medicine is taken by mouth as a pill. Side effects of imatinib are mostly mild to moderate. The most common side effect is mild nausea. Other side effects, usually mild as well, include diarrhea, fluid retention and swelling (often around the eyes), indigestion, muscle cramps, bleeding from the GIST tumor, fatigue, and a skin rash.

• Sunitinib. This medicine is often used when imatinib doesn't work or if the side effects of imatinib are a problem. Sunitinib can often cause tumors to shrink or stop them from growing for a time. It may help people with GIST live longer. It is taken by mouth as a pill. The most common side effects are diarrhea, mouth irritation, and changes in skin and hair color. More serious side effects can include high blood pressure, increased risk of bleeding, swelling, and heart and liver problems.

• Regorafenib. This drug is often used if other medicines are no longer working. It can often shrink tumors or slow their growth for a time. It is taken by mouth as a pill. Side effects can include diarrhea, feeling tired, high blood pressure, mouth sores, hair loss, loss of appetite, and problems with redness and pain in the palms of the hands and soles of the feet 

Other treatments, such as radiation therapy and chemotherapy, are used much less often. Your healthcare provider will talk with you about the treatment that can work best for you.