An Overview of Gastrointestinal Stromal Tumor

A gastrointestinal stromal tumor (GIST) is a disorder involving a group of cancers known as sarcomas. Sarcomas are very slow-growing malignant (potentially fatal) tumors of connective or other tissue, such as cartilage, nervous, and muscle tissue.

In the United States, there are an estimated 5,000 to 6,000 new diagnoses of GISTs each year. This type of tumor originates in nerve cells in the wall of the gastrointestinal (GI) tract and can occur anywhere from the esophagus to the rectum.

However, the most common type of gastrointestinal stromal tumor arises in the stomach and small intestine, therefore justifying its name. But GISTs have been reported as tumors arising from the gallbladder, pancreas, appendix, and the lining of the abdominal cavity.

Symptoms

Because GISTs commonly develop in empty spaces in the digestive tract (such as the stomach), they may initially cause no symptoms at all. Symptoms may not be seen until they reach a certain location, grow to a size large enough to press on nerves and cause pain, result in abdominal swelling, or obstruct the intestines.

Other symptoms of GIST may include:

• Bleeding into the large intestine, resulting in visible blood in the stool
• Vomiting blood, which may appear like coffee grounds
• Black, tarry stools, from bleeding into the stomach or small intestine
• Slow bleeding, which is often undetected and can result in anemia over time
• Fatigue and weakness, from slow bleeding

Other signs and symptoms of a GIST include:

• Abdominal pain
• A mass or enlarged abdomen
• Nausea and vomiting
• Bloating or the feeling of fullness after eating only small amounts
• Loss of appetite
• Weight loss
• Difficulty or painful swallowing (when tumors affect the esophagus)

The tumor may also produce symptoms of an abdominal obstruction if it blocks food from moving normally through the GI tract. These may include:

• Cramps
• Abdominal swelling
• Loss of appetite
• Constipation (inability to pass gas or have a bowel movement)
• Vomiting
• Severe abdominal pain (may be intermittent or constant)

Not only are GISTs prone to bleeding, the fragile nature of the tumors may cause them to rupture. This may lead to severe abdominal pain and an emergency that requires immediate surgery.

Anytime you experience unexplained abdominal pain (or other symptoms of an obstruction) for more than a few days, it’s important to consult with a healthcare provider right away.

Causes

Unlike other types of cancer, there are no known environmental causes of GISTs. Current research suggests that genetic abnormalities (mutations) underlie the processes by which cells become cancerous.

Gastrointestinal stromal tumors may be the result of specific genetic mutations (abnormal changes in genes). In fact, many groundbreaking discoveries about the genetic factors involved in cancer (in general) were discovered in studies involving gastrointestinal stromal tumors.

Cancer Development

Clinical research studies show that genetic mutations (abnormalities) may cause a cell to become cancerous.

According to the American Cancer Society, “malignancies most often develop due to mutations in genes known as ‘oncogenes’ or ‘tumor suppressor genes.’ Oncogenes promote cell division, while tumor suppressor genes block cell division and ensure that cells die at the proper time; abnormalities of either type of gene can contribute to cancer development.”

The Physiology of Cancer Cells

New cells are formed in the body during the cell-division cycle. But occasionally, errors (mutations) occur when the cells divide. These mutations happen when the cell mistakenly copies the DNA during the cell division process.

Tumor cells are different from normal cells in many aspects, including their growth rate, interaction with other cells, structure, gene expression, and more. When genetic mutations (mistakes) occur—particularly in specific types of genes, such as those that impact cell division—these mutations result in cells that don’t die when they should, or those that replicate (divide) too quickly, resulting in abnormal cells that don’t function properly.

Tumor cells may form malignant tumors, such as gastrointestinal stromal tumors. The tumor cells may eventually go on to develop the ability to migrate and spread to other areas of the body.

According to the American Cancer Society, most cancer-causing mutations are acquired, occurring randomly during a person’s lifetime, and are not inherited.

Diagnosis

Diagnosis of gastrointestinal stromal tumors is conducted by taking a patient history and performing a physical exam, in addition to imaging tests and lab tests to examine tissue (biopsy).

Specifically, the diagnostic procedures include:

• A physical examination to evaluate for general signs of illness, such as any lumps, abdominal swelling, or other unusual physical findings
• A patient history to gather information on overall health, lifestyle factors (such as smoking), past illnesses, surgeries, and previous treatments

Imaging Tests

Several imaging tests are performed as part of the process to diagnose gastrointestinal stromal tumors. These include:

• Computerized tomography (CT) scans: An imaging test that takes a series of pictures inside the body from various angles, a CT scan produces computerized X-ray images that can give very detailed illustrations of various body parts. A specific type of dye may be swallowed before the procedure, to enable the organs or tissues to show up more clearly.
• Magnetic resonance imaging (MRI): This imaging technique utilizes strong magnetic fields and radio waves to generate a series of detailed images of various areas inside the body. An MRI can show certain diseases (such as specific types of cancer) that are invisible using other types of imaging tests (such as a CT scan). An MRI is also better at detecting metastases (such as when cancer spreads to the bone or the brain).
• Endoscopic ultrasound and biopsy: An endoscope (a thin, tube-shaped instrument with a light, camera, and lens for viewing) is inserted into the mouth, then into the esophagus, the stomach, and the first part of the small intestine (the duodenum). Ultrasound (high-energy sound) waves are bounced off tissues and organs from a probe located at the end of an endoscope. This results in echoes that form an image (called a sonogram) of body tissues. Next, the surgeon uses a hollow needle to aspirate some tissue to send to the lab for a biopsy. The biopsy is a test to examine the tissue under a microscope to look for cancer cells.

Surgical Treatment

The primary method of treating gastrointestinal stromal tumors is surgery. The type of surgery and treatment methods following it depend on whether the tumor is resectable, unresectable, refractory, or if tumors metastasize or recur.

Resectable Tumors

If a tumor is considered “resectable,” it means that it can be entirely (or almost fully) removed surgically. Laparoscopic surgery—a type of abdominal surgery, using small incisions with the aid of a camera—may be performed for tumors that are 5 centimeters (1.9 inches) or smaller.

After surgery, tyrosine kinase inhibitor (TKI) drugs may be given to decrease the risk of the tumor coming back (recurring).

Unresectable Tumors

Treatment is aimed at shrinking the tumor if it is too large to be completely removed surgically, or if the tumor is located near an organ or structure that stands a high risk of being damaged during surgical removal of the tumor. 

Depending on the specific mutation present in the tumor, there are currently four FDA-approved drugs for the treatment of unresectable or metastatic GISTs: imatinib, sunitinib, regorafenib, and avapritinib. If the tumor progresses after use of these agents, other TKIs are recommended.

Drugs such as imatinib mesylate have an action of stopping the growth of tumor cells by blocking some of the enzymes needed for cell growth. Once the tumor has been adequately shrunk to a small enough size, a surgical procedure follows to remove as much of the tumor as possible.

Gastrointestinal Stromal Tumors That Metastasize or Recur

When GISTs metastasize (spread to other areas of the body) or recur (come back after initial treatment), treatment may include:

• Targeted therapy with imatinib mesylate or sunitinib
• Surgery, to remove tumors that have been shrunken down after treatment with targeted therapy
• Corrective surgery, to address serious complications such as bleeding, an intestinal blockage, an infection, or damage to the GI tract caused by the GIST
• A new type of treatment, such as one being administered in a clinical trial

Refractory Gastrointestinal Stromal Tumors

Refractory gastrointestinal stromal tumors are those that stop responding to medication after a while. In this instance, a new type of TKI drug may be used, or the patient may be referred to a clinical research trial that is testing the efficacy of a new drug.

Prognosis

A prognosis is an estimate—based on clinical research trial results—of how well a disease is expected to respond to treatment. For gastrointestinal stromal tumors, the relative five-year survival rate is around 90%.

The prognosis of a patient with primary GIST depends on tumor size, location, and cellular division.

For example, patients with stomach GISTs fare better than those with small intestine GISTs. The five-year survival rate is approximately 94% for GIST tumors that are localized to one organ and 52% for GIST tumors that are metastatic.

A Word From Verywell

When looking at survival rates for any type of cancer, it’s important to note that the statistics are based on previous outcomes of large numbers of people with the same type of cancer. These numbers cannot accurately predict every person’s individual situation. Be sure to discuss this information with your healthcare provider or other members of the cancer care team.