Gastrointestinal stromal tumors (GISTs) are tumors, or clusters of overgrown cells, in the gastrointestinal (GI) tract.

The GI tract is the body system responsible for digesting and absorbing food and nutrients. It includes your:

  • esophagus
  • stomach
  • small intestine
  • colon

GISTs begin in special cells that are part of your autonomic nervous system. These cells are located in the wall of the GI tract, and they regulate muscle movement for digestion.

The majority of GISTs form in the stomach. Sometimes they form in the small intestine. GISTs in the colon, esophagus, and rectum are much less common.

GISTs can be either malignant (cancerous) or benign (not cancerous).

The symptoms depend on the size of the tumor and where it’s located. Because of this, they often vary in severity and from one person to another.

Symptoms of GISTs can include:

  • bloody stools
  • pain or discomfort in the abdomen
  • nausea and vomiting
  • bowel obstruction
  • a mass in the abdomen that you can feel
  • fatigue or feeling very tired
  • feeling very full after eating small amounts
  • pain or difficulty when swallowing

Symptoms such as abdominal pain, nausea, and fatigue overlap with many other conditions.

If you’re experiencing any of these symptoms, you should talk with your doctor. They will help determine the cause of your symptoms.

If you have any risk factors for GISTs or any other condition that could cause these symptoms, be sure to mention that to your doctor.

Survival rates indicate the percentage of people with the same type and stage of GIST who are alive a certain period of time after their diagnosis.

For example, a localized 5-year survival rate of 93 percent means that people with this stage of GIST are, on average, about 93 percent as likely to survive for at least 5 years as people who don’t have GISTs.

Survival rates are based on statistics from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program database.

Keep in mind that survival rates are only estimates. Everyone’s body responds differently to GISTs and treatment.

Also be aware that relative survival rates don’t take into account recent improvements in treatment. They’re based on diagnosis and treatment for at least 5 years earlier.

Based on people diagnosed with GISTs between 2010 and 2016, the 5-year survival rates for each stage are as follows:

  • Localized: 93 percent
  • Regional: 80 percent
  • Distant: 55 percent
  • All stages combined: 83 percent

To diagnose a GIST, a healthcare professional will first ask you about your medical history and physically examine you.

If the doctor suspects you may have a GIST, any of the following tests may be performed to help diagnose it:

  • CT or CAT scan. This procedure takes specialized X-rays that provide detailed views of your GI tract.
  • MRI scan. As you lie still in an enclosed area, a magnet and radio waves make detailed images of your GI tract.
  • Upper endoscopy. An endoscope, a thin instrument with a light and lens, is inserted through your mouth into your upper GI tract, allowing your organs to be visually examined.
  • Endoscopic ultrasound (EUS). This procedure uses an endoscope with a probe that bounces ultrasound waves off your organs. This causes echoes that create a sonogram, an image of your body tissues.
  • Endoscopic ultrasound fine-needle aspiration (EUS-FNA) biopsy. By using an endoscope with a fine needle attached to it, your doctor can remove a small amount of tissue from the tumor for a biopsy.

Biopsy samples will be examined under a microscope by a pathologist, who may be able to determine whether the tumor is a GIST.

After you’re diagnosed with a GIST, further tests may be done to see if the cancer cells have spread to other parts of your body. These tests may include:

  • CAT scan
  • MRI
  • chest X-ray
  • positron emission tomography (PET) scan

A PET scan helps doctors locate malignant tumors in your body.

To do this, a healthcare professional will inject a small amount of radioactive glucose into a vein. A scanner then rotates around your body, taking a picture. In the picture, malignant tumor cells that are using more glucose will appear brighter.

The results of these tests will determine the treatment for your GIST.

The options for treating GISTs depend on whether the tumor can be surgically removed or if the cancer has metastasized (spread) to other parts of your body.

There are four standard types of GIST treatment:

  • Surgery. If the GIST hasn’t spread and it’s safe to do so, a healthcare professional may surgically remove the tumor and some surrounding tissue. A thin, lighted tube called a laparoscope may be used to make incisions and remove tissues.
  • Targeted therapy. Your doctor may prescribe drugs such as tyrosine kinase inhibitors (TKIs), which block signals for tumors to grow. These drugs are less harmful to healthy cells than chemotherapy or radiation.
  • Watchful waiting. A healthcare professional will monitor your condition but won’t prescribe treatment until there’s a change in your symptoms or signs.
  • Supportive care. To help improve your quality of life, you may receive supportive care if your GIST gets worse or you have side effects from treatments.

While targeted therapy with TKIs such as imatinib, sunitinib, and regorafenib may be effective, secondary KIT or PDGFRA mutations develop that are resistant to these drugs in 90 percent of GIST cases. Most GIST growth is driven by KIT or PDGFRA mutations.

In 2020, the Food and Drug Administration (FDA) approved the following new drug treatments for people with GIST who received prior treatment with TKIs:

  • avapritinib (Ayvakit), the first drug approved for treating GIST with a PDGFRA exon 18 mutation, including D842V mutations
  • ripretinib (Qinlock), the first drug approved as a fourth-line treatment for advanced GIST

The exact cause of GISTs isn’t known, though they seem to be related to a mutation in the expression of the KIT protein.

Cancer develops when cells begin to grow out of control. As the cells continue to grow uncontrollably, they build up to form a mass called a tumor.

GISTs start in the GI tract and can grow outward into nearby structures or organs. They frequently spread to the liver and peritoneum (the lining of the abdominal cavity) but rarely to nearby lymph nodes.

There are only a few known risk factors for GISTs:

Age

The most common ages to develop a GIST is between 50 and 80 years old. While GISTs can happen in people younger than age 40, they’re extremely rare.

Genes

The majority of GISTs happen randomly and have no clear cause. However, some people are born with a genetic mutation that can lead to GISTs.

Some of the genes and conditions associated with GISTs include:

Neurofibromatosis 1

This genetic disorder, also called Von Recklinghausen’s disease (VRD), is caused by a defect in the NF1 gene. The condition can be passed from parent to child but isn’t always inherited. People with this condition are at an increased risk to develop benign tumors in nerves at an early age. These tumors can cause dark spots on the skin and freckling in the groin or underarms. This condition also increases the risk for developing a GIST.

Familial gastrointestinal stromal tumor syndrome

This syndrome is caused most often by an abnormal KIT gene passed from parent to child. This rare condition increases the risk of GISTs. These GISTs can form at a younger age than in the general population. People with this condition can have multiple GISTs during their lifetime.

Mutations in the succinate dehydrogenase (SDH) genes

People born with mutations in the SDHB and SDHC genes are at an increased risk for developing GISTs. They’re also at increased risk for developing a type of nerve tumor called a paraganglioma.

GISTs are a rare form of cancer that are usually benign. Depending on the size and location of your GIST, it may be surgically removed and you’ll likely make a full recovery.

Improvements in targeted drug therapies may help improve the survival rates for people whose GISTs have become resistant to other drugs.

Clinical trials help determine whether a new medical treatment is effective for treating diseases. You can see if there are any clinical trials of treatments for GIST on the National Cancer Institute (NCI) website.

The NCI website also provides a list of resources that may help you cope with a GIST diagnosis and treatment.