A gastrointestinal stromal tumor (GIST) is a type of tumor that occurs in the gastrointestinal (GI or digestive) tract, including the esophagus, stomach, gallbladder, liver, small intestine, colon, and rectum. GIST is a rare tumor that differs from other types of gastrointestinal tumors because of the type of tissues in which it starts. Originally, GISTs were thought to be either muscle or nerve tumors, but recent research points to GISTs starting in cells found in the walls of the GI tract, called interstitial cells of Cajal (ICC); these cells send signals to the GI tract to help move food and liquid through the system. GISTs belong to a group of cancers called soft tissue sarcoma. Sarcoma occurs in connective tissues such as muscle, fat, nerves, blood vessels, cartilage, and bone.
It is important to note that GISTs can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). Sometimes it may be hard for the doctor to tell immediately whether a GIST is cancerous. As a result, the doctor will look at many factors to determine the best treatment, including the size of the tumor, whether it is spreading, how many dividing cells there are, and the tumor’s location.
Statistics
In 2008, approximately 4,500 to 6,000 adults in the United States will be diagnosed with GISTs. They occur most commonly in the stomach (50% to 70%) and small intestine (20% to 30%). The remaining types of GISTs affect the large intestine and esophagus. Most GISTs occur in people older than 50, and GIST is more common in men than in women.
Cancer statistics should be interpreted with caution. Estimates are based on data from thousands of cases of this type of cancer in the United States each year, but the actual risk for a particular individual may differ. It is not possible to tell a person how long he or she will live with a gastrointestinal stromal tumor. Because the survival statistics are measured in five-year (or sometimes one-year) intervals, they may not represent advances made in the treatment or diagnosis of this cancer.
A risk factor is anything that increases a person’s chance of developing cancer. Some risk factors can be controlled, such as smoking, and some cannot be controlled, such as age and family history. Although risk factors can influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and communicating them to your doctor may help you make more informed lifestyle and health-care choices.
The only known risk factor for GIST is family history of the disease, when there is a small increase in risk of developing GIST. GIST is frequently associated with mutations in the KIT gene, and less commonly with mutations in a related gene called PDGFRA. The majority of these mutations are found only in the tumor tissue itself and cannot be inherited through a family. However, some families with inherited mutations in the KIT gene have been identified. In addition to multiple occurrences of both benign and malignant GIST, many of these families are also found to have increased skin pigmentation (coloring) under the arms, on the hands and face, and on the perineal skin (the area between the rectum and the genitals). There have also been families described with heritable mutations in the KIT gene that have only GIST and no unusual pigmentation. In all families with KIT mutations, GIST develops in adulthood. It is likely that there are other genes that have not yet been identified that play a role in the development of GIST.
In addition, a new inherited syndrome characterized by multiple gastric (stomach) stromal tumors and multiple paragangliomas (tumors on the nerves; primarily in the neck, chest, and abdominal wall) has been proposed, and research is ongoing. The gene associated with this condition has not yet been identified.
Approximately 7% of people with the hereditary syndrome neurofibromatosis type 1 (NF1) have GIST. The most common features of NF1 are multiple neurofibromas (tumors starting in nerves that cause lumps. These lumps often cause nodules on the skin of affected people), freckling under the arms and in the groin area, multiple café-au-lait spots (areas of light brown pigmentation) on the skin, and a symptom affecting the iris of the eye, called Lisch nodules. The gene associated with NF1 is also called NF1.
The KIT gene mutations, the newly described syndrome of GISTs and paragangliomas, and NF1 all follow an autosomal dominant inheritance pattern, in which a mutation happens in only one copy of the gene. This means that a parent with a mutation may pass on a copy of their working gene or a copy of their altered gene. Therefore, a child who has a parent with a mutation has a 50% chance of inheriting that mutation.
Because no other controllable risk factors have been identified, there is no way to prevent GIST.
People with GIST may experience the following symptoms. Sometimes, people with GIST do not show any of these symptoms. Or, these symptoms may be caused by a medical condition that is not cancer. If you are concerned about a symptom on this list, please talk with your doctor. GISTs are not usually found at an early stage because they often do not cause specific symptoms. When symptoms do occur, they may be vague and can include:
Doctors use many tests to diagnose a tumor and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of tumors, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:
Age and medical condition
The type of tumor suspected
Severity of symptoms
Previous test results
In addition to a physical examination, the following tests may be used to diagnose GIST:
Blood/urine tests. Several laboratory tests may be conducted, including a blood test to check several organ functions and a urine test to detect protein, sugar, or other abnormalities.
Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a vein to provide better detail. For patients with GIST, the CT scan is the most commonly used diagnostic tool. A CT scan can help doctors determine whether the cancer has spread to the liver.
Fecal occult blood test. This test detects occult (hidden) blood in the stool, which can be caused by cancer in the GI tract. A small amount of stool is placed on a plastic slide or special paper and is tested in the doctor's office or a laboratory.
X-ray. An x-ray is a picture of the inside of the body. For instance, a chest x-ray can help doctors determine if the cancer has spread to the lungs. X-rays may be taken of the esophagus and stomach, which are referred to as the upper GI tract. This procedure is also called a barium swallow, because the x-rays are taken after a patient drinks a substance called barium, which outlines the GI tract on the x-ray and helps the doctor see a tumor or other abnormal areas. In a barium enema, the doctor looks at the lining of the colon and rectum on the x-ray after the barium is administered through the anus.
Endoscopy. This test allows the doctor to see the inside of the stomach. The patient may be sedated, and the doctor inserts a thin, lighted tube called a gastroscope through the mouth, down the esophagus, and into the stomach and small bowel. If abnormal areas are found, the doctor can remove a sample of tissue and check it for evidence of cancer.
Endoscopic ultrasound. This test is similar to an endoscopy, but the gastroscope has a small ultrasound probe on the end that uses sound waves to create an image of the stomach. The ultrasound image helps doctors determine if or how far the cancer has spread into the stomach and nearby tissues.
Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium may be injected into a patient’s vein to create a clearer picture.
Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. PET scans are often used to complement information gathered from CT scan, MRI, and physical examination, and may be used to document early growth of the disease (called PET flare), or to measure the tumor’s early response to treatment.
Biopsy. It is vitally important to be seen by a team of medical and surgical oncologists experienced in the treatment of GIST before any surgery or biopsy are performed. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. The sample removed from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). The type of biopsy performed will depend on the location of the cancer. In the case of GIST, the patient may still be monitored even if the biopsy results do not indicate cancer, as a biopsy for GIST is not always definitive.
Staging is a way of describing a cancer, such as where it is located, whether it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer's stage, so staging may not be complete until all the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of cancers.
There is no standard staging system for GIST; however, the two most common factors in determining the risk of a GIST being cancerous are the size of the tumor and the mitotic count (the actual number of dividing cells). The following table was developed from the Gastrointestinal Stromal Tumor (GIST) Workshop:
Proposed Approach for Defining Risk of Aggressive Behavior in GISTs
The treatment of GIST depends on the size and location of the tumor, if it is cancerous, whether the cancer has spread, and the person’s overall health. In many cases, a team of doctors will work with the patient to determine the best treatment plan.
This section outlines treatments that are the standard of care (the best treatments available) for this specific type of cancer. Patients are also encouraged to consider clinical trials as a treatment option when making treatment plan decisions. A clinical trial is a research study to test a new treatment to prove it is safe, effective, and possibly better than standard treatment. Your doctor can help you review all treatment options. For more information, visit the Clinical trials section.
Surgery
For patients with GIST, surgery is the standard of care and should be performed whenever possible. The goal of surgery is to completely remove the tumor. Sometimes the tumor may be large or spread into nearby organs. In many of these cases, a drug called imatinib (see below) will be given before surgery. The surgeon will most likely still try to remove the entire tumor in an effort to reduce the risk that the tumor will recur (come back after treatment) or block the GI tract. In order to remove the entire tumor, it is possible that the surgeon may have to remove parts of nearby organs, depending on the location of the tumor. The removal of lymph nodes is not generally needed in the treatment of a GIST because it does not often spread to the lymph nodes.
Targeted therapy
Targeted therapy is a treatment that targets faulty genes or proteins that contribute to cancer growth and development. In 2002, the U.S. Food and Drug Administration (FDA) approved imatinib (Gleevec) for the treatment of GIST. Imatinib is a tyrosine kinase inhibitor, and is the drug of choice in treating GIST. It is usually given as either the only treatment or in combination with surgery (before or after surgery). It is a cytostatic agent, which stops tumor growth, rather than cytotoxic, such as conventional chemotherapy, which kills fast-growing cells. Therefore, the medication will be taken by patients for a prolonged period of time. Since this drug has become available, the prognosis for patients with GIST has improved considerably. The usual dose of imatinib is 400 milligrams (mg) daily. In some patients the dose can be raised to 800 mg daily. Sunitinib (Sutent), like imatinib, is a tyrosine kinase inhibitor with anti-angiogenic (a form of targeted therapy that stops tumors from creating new blood vessels) properties, and it was approved in 2006 by the FDA for treating GIST when the tumor continues to grow even after treatment with imatinib, or in cases where imatinib cannot be given.
The medications used to treat cancer are continually being evaluated. Talking with your doctor is often the best way to learn about the medications you’ve been prescribed, their purpose, and their potential side effects or interaction with other medications. Learn more about your prescriptions through Drug Information Resources, which provides links to searchable drug databases.
Radiation therapy
Radiation therapy is the use of high-energy x-rays or other particles to kill cancer cells. The most common type of radiation treatment is called external-beam radiation therapy, which is radiation given from a machine outside the body.
In GIST, radiation therapy is not effective for treating the tumor itself, but may be used as a palliative treatment (treatment used to reduce pain, control symptoms, or make a patient more comfortable) to relieve pain. Radiation therapy, like chemotherapy, may damage healthy cells as well as cancerous cells. Side effects from radiation therapy include tiredness, mild skin reactions, upset stomach, and loose bowel movements. Most side effects go away soon after treatment is finished.
Chemotherapy
Chemotherapy is the use of drugs to kill cancer cells. Chemotherapy is not effective in treating GIST; therefore, it is not used.
Doctors and scientists are always looking for better ways to treat patients with GIST. A clinical trial is a way to test a new treatment to prove that it is safe, effective, and possibly better than a standard treatment. Patients who participate in clinical trials are among the first to receive new treatments before they are widely available. However, there is no guarantee that the new treatment will be safe, effective, or better than a standard treatment.
Patients decide to participate in clinical trials for many reasons. For some patients, a clinical trial is the best treatment option available. Because standard treatments are not perfect, patients are often willing to face the added uncertainty of a clinical trial in the hope of a better result. Other patients volunteer for clinical trials because they know that finding new drugs and other therapies is the only way to make progress in treating GIST. Even if they do not benefit directly from the clinical trial, their participation may benefit future patients with GIST.
To join a clinical trial, patients must complete a learning process known as informed consent. During informed consent, the doctor should list all of the patient’s options, so the person understands how the new treatment differs from the standard treatment. The doctor must also list all of the risks of the new treatment, which may or may not be different from the risks of standard treatment. Finally, the doctor must explain what will be required of each patient in order to participate in the clinical trial, including the number of doctor visits, tests, and the schedule of treatment. Learn more about clinical trials, including patient safety, phases of a clinical trial, deciding to participate in a clinical trial, questions to ask the research team, and links to find cancer clinical trials.
A tumor and its treatment can cause a variety of side effects. However, doctors have made major strides in recent years in reducing pain, nausea and vomiting, and other physical side effects of treatments. Many treatments used today are less intensive but as effective as treatments used in the past. Doctors also have many ways to provide relief to patients when such side effects do occur.
Fear of treatment side effects is common after a diagnosis of GIST, but it may be helpful to know that preventing and controlling side effects is a major focus of your health-care team. Before treatment begins, talk with your doctor about possible side effects of the specific treatments you will be receiving. The specific side effects that can occur depend on a variety of factors, including the type of tumor, its location, the individual treatment plan (including the length and dosage of treatment), and the person’s overall health.
Ask your doctor which side effects are most likely to happen (and which are not), when side effects are likely to occur, and how they will be addressed by the health-care team if they do happen. Also, be sure to communicate with the doctor about side effects you experience during and after treatment. For more information on the most common side effects of a tumor and different treatments, along with ways to prevent or control them, visit Cancer.Net’s section on Managing Side Effects, based on ASCO’s curriculum.
In addition to physical side effects, there may be psychosocial (emotional and social) effects as well. Learn more about the importance of addressing these needs in Cancer.Net’s section on Caring for the Whole Patient.
For more information on late effects or long-term side effects, please read the After Treatment section or talk with your doctor.
After treatment for GIST ends, talk with your doctor about developing a follow-up care plan. This plan will include regular physical examinations and medical tests to monitor your recovery over the coming months and years. A person treated for GIST is typically seen by the doctor every three to six months for up to five years and then annually after that. This follow-up care is important because there is always a risk that the tumor could recur, even after extensive surgery.
People recovering from GIST are encouraged to follow established guidelines for good health, such as maintaining a healthy weight, not smoking, eating a balanced diet, and having recommended cancer screening tests. Talk with your doctor to develop a plan that is best for your needs. Moderate physical activity can help rebuild your strength and energy level. Your doctor can help you create an appropriate exercise plan based upon your needs, physical abilities, and fitness level. Learn more about Healthy Living After Cancer.
Research for GIST is ongoing. The following advances may still be under investigation in clinical trials and may not be approved or available at this current time. Always discuss all diagnostic and treatment options with your doctor.
Personalized medicine. Recent studies have shown that depending on genetic findings (specific gene mutations), some patients may require higher doses of imatinib to achieve the best results. Currently this testing is being offered in clinical trials. Also, because the exact type of gene mutations in GIST is an important indicator of the tumor’s treatment response to both imatinib and sunitinib, obtaining this information from individual patients may, therefore, allow therapy to be targeted based on the specific mutation present in the tumor. This may fine-tune the most appropriate therapy to be administered in early stage of the tumor.
Regular communication with your doctor is important in making informed decisions about your health care. Consider asking the following questions of your doctor:
General questions:
Where is the tumor located?
Can you explain my pathology report to me?
How aggressive is the tumor? Is it cancerous?
Are additional treatments needed to determine if the tumor is cancerous?
Should I be seeing a GIST specialist?
What are my treatment options?
What clinical trials are open to me?
What is the goal of each option?
What treatment do you recommend? Why?
What are the possible side effects of this treatment, both in the short term and the long term?
How will this treatment affect my daily life? Will I be able to work, exercise, and perform my usual activities?
Do I need treatment right away?
Questions to ask before surgery:
Can you describe this surgery to me?
What are the possible side effects of this surgery?
Will I need to stay in the hospital for this surgery? For how long?
Does the stage of cancer affect the decision for surgery? How?
Questions about imatinib mesylate (Gleevec):
If I have surgery, should I take Gleevec before surgery? What dosage? For how long?
If I have surgery, should I take Gleevec after surgery? What dosage? For how long?
What factors determine how effective Gleevec is likely to be?
What can be done if Gleevec stops working? Can I receive Sutent in that case?
Questions to ask before radiation therapy:
What kind of radiation therapy is recommended?
What does the preparation for this treatment involve?
What other side effects can I expect from this treatment?
What can be done to treat the side effects?
After treatment:
What are the chances that the cancer will return?
What follow-up tests do I need, and how often do I need them?
What support services are available to me? To my family?
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