What is a GIST?

A gastrointestinal stromal tumor (GIST) is a rare type of cancer. It occurs in the gastrointestinal (GI) or digestive tract. A tumor can happen anywhere in your GI tract, from the esophagus to the anus.

GIST starts in cells that 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.

Who is at risk for GIST?

Researchers are still learning what causes GIST. In most cases, a gene change (mutation) causes the cells to grow out of control. This causes a tumor to grow.

A risk factor is anything that may increase your chance of having a disease. The exact cause of someone’s cancer may not be known. But risk factors can make it more likely for a person to have cancer. Some risk factors may not be in your control. But others may be things you can change.

Anyone can get GIST. But certain genetic syndromes passed in families have been linked to a higher risk. These include:

• Neurofibromatosis type 1 (NF1)

• Carney triad

What are the symptoms of GIST?

Many people with GIST have vague symptoms. As the tumor grows, symptoms may include:

• Discomfort or pain in the stomach

• Vomiting

• Blood in stools or vomit

• Feeling very tired (from low levels of red blood cells, a condition called anemia)

• Feeling full after eating only a small amount

• Trouble or pain when swallowing

• Loss of appetite

• Weight loss

Many of these may be caused by other health problems. Still, it's important to see a healthcare provider if you have these symptoms. Only a healthcare provider can tell if you have cancer.

How is GIST diagnosed?

Your healthcare provider will ask about your medical history, your symptoms, and your family history. A physical exam will be done. You may also have some tests, such as:

• Blood tests. These help your provider get an idea of your overall health and how well certain organs are working.

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

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

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

• Biopsy. Tiny pieces of tissue (called a sample) are taken from the tumor. They're sent to a lab and tested for cancer. A biopsy may be done during endoscopy. Or the sample may be removed during surgery.

How is GIST treated?

GIST can be treated in many ways. It grows differently in each person. The type of treatment that's 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. When GIST spreads, it tends to go to the liver and the lining of the stomach.

GIST may be treated with:

• Surgery. If the cancer has not spread, surgery can be done to remove the tumor and a healthy edge of tissue around it.

• Targeted therapy. These medicines target certain parts of cancer cells that make them unlike normal cells. They're very helpful in treating GIST. Targeted therapy doesn't work the same as chemotherapy and causes different side effects.

The medicines most commonly used to treat GIST are taken as pills at home. They include:

• Imatinib. This is often the first medicine used for GIST. It can be given before surgery to try to shrink the tumor so it's easier to remove. It can also be used 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.

• Sunitinib. This medicine is often used when imatinib doesn't work or if the side effects of imatinib become a problem. It can often shrink tumors or stop them from growing for a time. It may help people with GIST live longer.

• Regorafenib. This medicine is often used for advanced GIST if other medicines are no longer working or can't be taken for some reason. It can often shrink tumors or slow their growth for a time.

• Ripretinib. This medicine might be used for advanced GIST if other targeted therapies stop working. It can help slow tumor growth and even shrink tumors for a time.

• Avapritinib. This medicine targets a gene change called an exon 18 mutation. It might be used if tests show that your cancer cells have this mutation. GISTs with this mutation don't usually respond well to other targeted therapy medicines.

Other treatments, like radiation therapy and chemotherapy, are seldom used to treat GIST.

Talk with your healthcare providers about your treatment options. Make a list of questions. Think about the benefits and possible side effects of each option. Talk about your concerns with your healthcare provider before making a decision.

What are treatment side effects?

Surgery can cause side effects like pain, bleeding, and infection. Your providers will talk with you about these before you have surgery. Side effects depend on the type of surgery done and where the tumor is.

Targeted therapy medicines also cause side effects. These depend on which medicine is used. They can include:

• Nausea

• Diarrhea

• Loss of appetite

• Fluid retention and swelling

• Muscle cramps

• Bleeding from the GIST tumor

• Feeling very tired (fatigue)

• Skin rash

• Changes in skin and hair color

• Redness and pain in the palms of the hands and soles of the feet 

• Hair loss

• Blood pressure changes

In most cases, side effects are mild to moderate. And there are often ways to manage them. More serious side effects can include high blood pressure, increased risk of bleeding, swelling, and heart, lung, or liver problems.

When to call the healthcare provider

It's important to know which medicines you're taking. Write down the names of your medicines. Ask your healthcare team how they work, how to take them, and what side effects they might have.

Talk with your healthcare providers about what signs to look for and when to call them. For example, imatinib can cause itchy skin rashes that can lead to infections. Make sure you know what number to call with questions. Is there a different number for evenings and weekends?

It may be helpful to keep a diary of your side effects. Write down the physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your healthcare team to make a plan to manage your side effects.