Gastrointestinal stromal tumors (GISTs) start in cells located in the walls of the digestive (gastrointestinal, or GI) tract. The digestive tract includes the stomach, small intestine, and large intestine (colon). The cells of the GI tract help control the contraction and expansion of muscles within our digestive tract. These cells are important for moving food and liquid through the body for digestion, energy, and the removal of waste.

More than half of GISTs start in the stomach. Many others begin in the small intestine. However, gastrointestinal stromal tumors can grow anywhere along the digestive tract. A small number of GISTs start outside the GI tract, in the appendix, gallbladder, or pancreas, for instance.

Types of Gastrointestinal Stromal Tumors

• Resectable gastrointestinal stromal tumors
• Unresectable gastrointestinal stromal tumors
• Metastatic and recurrent gastrointestinal stromal tumors
• Refractory gastrointestinal stromal tumors

Tests

Along with a physical and medical history review, the following tests and procedures may be used:

CT (Computed Tomography) Scan
A procedure that makes a series of detailed pictures of areas inside the body, 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.

MRI (Magnetic Resonance Imaging)
A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).

Endoscopic Ultrasound and Biopsy
Endoscopy and ultrasound are used to make an image of the upper GI tract and take a biopsy. An endoscope (a thin, tube-like instrument with a light and a lens for viewing) is inserted through the mouth and into the esophagus, stomach, and first part of the small intestine. A probe at the end of the endoscope is used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. Guided by the sonogram, the doctor removes tissue using a thin, hollow needle. A pathologist views the tissue under a microscope to look for cancer cells.

Immunohistochemistry
A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.

Mitotic Rate
This test measures how fast the cancer cells are dividing and growing. The mitotic rate is found by counting the number of cells dividing in a certain amount of cancer tissue.

Treatments

Four standard therapies are used in the treatment of gastrointestinal stromal tumors:

Surgery
If the GIST has not spread and is in a safe place for surgery, it may be removed using laparoscopic surgery. Some tissue around the tumor also will be removed. The laparoscope is a thin, lighted tube that helps a surgeon see inside the body. Very small “keyhole” incisions (cuts) are made in the wall of the abdomen. The laparoscope is inserted into one of the incisions, as is a surgical instrument to remove the cancerous tissue.

Targeted Therapy
Targeted therapy uses drugs or other substances to find and attack a specific type of cancer cell without harming healthy cells. Tyrosine kinase inhibitors (TKIs) are targeted therapy drugs that block signals needed for tumors to grow. TKIs may be used to treat GISTs that cannot be removed by surgery. They may also be used to shrink GISTs before a surgery. Imatinib mesylate and sunitinib are two TKIs used to treat GISTs.

Active Surveillance (Watchful Waiting)
Sometimes your doctor may recommend waiting on treatment. This is called active surveillance, or watchful waiting. If we believe it is best to wait for more signs or symptoms before treating a GIST, we will continue monitoring your condition through regularly scheduled testing.

Supportive Care
Supportive care may be offered if your tumor gets worse or if you have additional side effects of the tumor or your treatment. It can include pain management, psychological, social, and spiritual support. The goal is to help improve the quality of life for patients who have a serious or life-threatening disease.

• Radiation therapy is one supportive care treatment that could be recommended to relieve pain in patients with large GIST tumors that have spread.

Clinical Trials
If your doctor believes you would benefit from enrollment in a clinical trial, he or she will discuss that option with you. Clinical trials are investigative studies of the newest available drugs, drug combinations or surgical approaches to treat a specific tumor.

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Sylvester is an NCI-designated cancer center. The National Cancer Institute has recognized Sylvester for its outstanding work conducting research in its laboratories, treating patients in its clinics and hospitals, and reaching out to medically underserved communities with innovative prevention strategies.

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