Gastrointestinal stromal tumors (GISTs) are a rare type of cancer that begins in the gastrointestinal (GI) tract. In the early stages, the tumors usually don’t cause many symptoms. However, when symptoms do appear, they can be mistaken for other gastrointestinal diseases and conditions. Because GIST is a rare condition, these other conditions should be ruled out before more specific testing leads to a GIST diagnosis.
Tests and diagnosis
Doctors may use the following tests and procedures to diagnose GISTs:
During a physical exam, your doctor checks for overall signs of health. The exam is a general overview of how you’re feeling. If you have an unusual symptom, like a lump or a bruise, your doctor will look at it more closely. If you’re noticing something unusual with your body, this is a good time to bring it up with your doctor.
Fecal occult blood test
This test looks for small traces of blood in your stool that can’t be seen. Blood in the stool can be caused by cancer in the GI tract, or may be a sign of other conditions.
A CT scan takes a series of detailed pictures of a specific area inside the body. An X-ray machine connected to a computer takes the pictures, often from many angles, to create cross-sectional images of a certain area of the body. Sometimes a dye is used to help the tissues inside the body appear more clearly on imaging. The dye may be swallowed or injected.
This procedure uses magnetic waves and a computer to take pictures of areas inside the body. A dye is often given before the scan to help make the picture clearer. These pictures can be very detailed, and may be better that a CT scan in certain situations.
This is another way to take pictures of organs and tissues inside the body without using an X-ray. A small amount of radioactive sugar is injected into the body. A scanner detects the substance and uses it to make images. The substance is absorbed more by cells using high levels of energy, such as cancer cells. This is why it’s useful for detecting cancer.
An endoscopic ultrasound uses sound waves from a probe to create pictures of the GI tract. A doctor will insert the probe through the mouth, down the esophagus, and into either the stomach or small intestine. The probe has a light and a lens attached for viewing. This procedure usually happens along with a biopsy. It’s used to visualize the tumor.
A biopsy involves the removal of a small amount of tissue from the body. The tissue is then examined under a microscope. Doctors use biopsies to look at tumor cells for evidence of cancer.
If your doctor finds cancer cells during one of the tests, they may order a follow-up test. The following tests are used to learn more about the cancer:
- Pathology: This test is a visual examination of the GIST under a microscope to look at the shape and appearance of the tumor cells.
- Mitotic count: This test measures how fast the tumor cells are growing and dividing. It’s used to predict prognosis.
- Molecular testing: This is a category of tests that can look for the presence or absence of certain proteins or genetic mutations in the tumor cells. These proteins or genetic mutations may affect treatment.
Once a diagnosis of a GIST has been made, the next step is staging the cancer. Staging allows your doctor and treatment team to plan your treatment. It can also help them understand your prognosis and likelihood of recovery.
Initially, common factors used to stage a GIST include:
- size of the tumor
- mitotic count, or how fast the cells are growing and dividing
- where the tumor started
- metastasis, or if the tumor has spread to other parts of the body
In recent years, the more conventionally used TNM (tumor-node-metastasis) system for staging cancer has been applied to staging GISTs. This has become possible as more data on GIST has been collected and studied.
There are different types of treatments for GISTs. Many are available commercially, but other treatments are available only through clinical trials or research studies.
Some current treatments include:
- Surgery: Surgery for a GIST involves removing the whole tumor and surrounding tissue. This ensures that no cancer cells are left behind. When the GIST is localized, or hasn’t spread to other parts of the body, surgery is the standard treatment and should be performed if possible.
- Targeted therapy: Targeted therapy is a much newer type of treatment that can more precisely identify and attack cancer cells. Because of this, targeted therapies are thought to have fewer side effects than traditional cancer treatments.
- Tyrosine kinase inhibitors (TKIs): TKIs are a specific type of drug used to treat GISTs by blocking signals that cells need to grow. TKIs are used for GISTs that can’t be removed by surgery or that need to be shrunk before removal. Some TKIs used for treatment include imatinib (Gleevec), regorafenib (Stivarga), and sunitinib (Sutent).
For those with a terminal diagnosis, palliative care is another treatment choice. The goal of palliative care is to alleviate symptoms of an illness to improve quality of life. Palliative care can involve pain management, counseling, and many other interventions. This type of care is managed by a team of doctors, nurses, pharmacists, psychologists, and other healthcare professionals.
Radiation and chemotherapy are two other common cancer treatments, but aren’t typically used to treat people with GISTs. However, radiation can be used as a form of palliative treatment. Chemotherapy uses chemicals to destroy cancer cells by stopping their ability to grow. This therapy isn’t effective in treating GISTs.
Your healthcare team will take into account your test results, tumor stage, and personal preferences when determining the best treatment plan for you.