Gastrointestinal stromal tumor, or GIST, is a rare type of sarcoma that forms along the gastrointestinal tract, but mostly starts in the stomach or small intestine.
We often don’t know why certain people develop GIST. In some cases, though, risk factors can increase your chances of developing this disease. The primary risk factor for GIST is genetics, meaning that the cancer can run in families. Certain genetic syndromes may also be GIST risk factors, including:
- Neurofibromatosis type 1: This disease is caused by a defect in the NF1 gene. This gene change may be inherited from a parent, but in some cases it occurs before birth, without being inherited.
- Carney triad: People with this rare, inherited condition have an increased risk of GISTs (most often in the stomach), as well as nerve tumors called paragangliomas. GISTs often develop when these people are in their teens or 20s. They are also more likely to have more than one GIST.
Most patients with GIST do not have any specific symptoms. GIST symptoms are common to a variety of different problems. Check with your doctor if you experience any of the following:
- Blood in your vomit or stool
- Severe stomach pain
- Painful swallowing
- Your stomach feels full even after eating just a small amount
To determine if you are suffering from a GIST tumor, as well as whether it is surgically removable, your surgical oncologist will perform a number of diagnostic tests, including:
- Physical exam and history : An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the chest, abdomen, and pelvis, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
- Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. An abdominal ultrasound is done to diagnose GIST.
- Chest X-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. The biopsy may be done after surgery to remove the tumor. If the tumor clearly cannot be removed by surgery, the biopsy may be done using a fine needle to remove cells from the tumor.
- MRI: MRI scans use radio waves and strong magnets instead of X-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. These scans can help oncologists find the extent of the cancer in the abdomen
Doctors use a staging system to describe the extent of spread of most types of cancer, including gastrointestinal stromal tumors (GISTs). The most common system used is the TNM system of the American Joint Committee on Cancer (AJCC). This system is based on 4 key pieces of information:
- T describes the size of the primary tumor, measured in centimeters (cm).
- N describes whether the cancer has spread to nearby (regional) lymph nodes (this is very rare for GISTs).
- M indicates whether the cancer has metastasized (spread) to other organs of the body. If a GIST does spread, most often it is within the abdomen, such as to the liver. Less often, it may spread to the lungs and bones.
- The mitotic rate is a measure of how fast the cancer cells are growing and dividing. It is described as either low or high. A low mitotic rate predicts a better outcome.
Numbers or letters appear after T, N, and M to provide more details about each of these factors:
- The numbers 0 through 4 indicate increasing severity.
- The letter X means “cannot be assessed” because the information is not available.
Stage I: T1 or T2, N0, M0, low mitotic rate: The tumor is no larger than 5 cm across (T1 or T2). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.
Stage II: T3, N0, M0, low mitotic rate: The tumor is larger than 5 cm but not larger than 10 cm across (T3). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.
Stage IIIA: One of the following applies:
T1, N0, M0, high mitotic rate: The tumor is no larger than 2 cm across (T1). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.
T4, N0, M0, low mitotic rate: The tumor is larger than 10 cm across (T4). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.
Stage IIIB: T2 to T4, N0, M0, high mitotic rate: The tumor is larger than 2 cm across (T2 to T4). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.
Stage IV: One of the following applies:
Any T, N1, M0, any mitotic rate: The tumor can be any size (any T) and the cancer has spread to nearby lymph nodes (N1). It has not spread to distant sites (M0). The tumor can have any mitotic rate.
Any T, any N, M1, any mitotic rate: The tumor can be any size (any T) and it may or may not have spread to nearby lymph nodes (any N). The cancer has spread to distant sites, such as the liver or the lungs (M1). The tumor can have any mitotic rate.
Because GIST is so rare, few doctors have experience treating it. Through MedStar Health, however, MedStar Washington Hospital Center has become one of the country's major centers for the clinical study of GIST, and serves as a site for clinical trials that have revolutionized fighting the disease.
Surgery is the standard treatment, but not all GISTs can be removed. About a decade ago, patients diagnosed with recurrent or metastatic GIST had few treatment options or hope for survival. Today, the outlook is more promising.
Your treatment options for GIST depend on two factors:
- Whether a surgical procedure can remove your tumor
- Whether your tumor is spreading to other parts of your body
Depending on these factors, your specialist may recommend:
- Surgery: This is the prime option for GIST tumors that have not spread to other areas of the body. Surgical oncologists can completely remove the tumor, as well as surrounding tissue.
- Targeted therapy before surgery: This treatment uses special drugs to locate the tumor and destroy cancer cells. Targeted therapy can help shrink very large tumors so your surgeon can then remove them with surgery. Imatinib is the most commonly used targeted therapy for GIST.
- Targeted therapy after surgery: For some patients, we recommend targeted therapy after surgical removal of your GIST. To determine whether you need this treatment, we evaluate your pathology report, and factor in your tumor size and mitotic count. We also work closely with our multidisciplinary team of specialists to determine the best course of therapy for you.
Surgery is the standard treatment, but not all GISTs can be removed. Our clinical trials have studied the newest drugs available to target GIST, including imatinib, sunitinib and nilotinib. MedStar Washington Hospital Center’s cancer team was among the first to study imatinib, the first targeted therapy developed for GIST.
Please note: These drugs do not cure the disease, but they do help somecan stop tumors stopfrom growing or, even better, to shrink, which has extended. This helps extend the survival rate fortime of patients with recurrent or metastatic GIST.
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