Gastrointestinal Stromal Tumor (GIST)

A gastrointestinal stromal tumor, or GIST, is a tumor that grows from special nerve cells present in the walls of the digestive organs. These cells help move food through the body. 

The interstitial cells of Cajal are a specialized type of cell found in the gastrointestinal (GI) tract. These cells help regulate food and liquid movement in the digestive system and coordinate smooth muscle contractions. Although it can occur at any age, GIST is most commonly diagnosed later in life, with a median age of diagnosis in the 60s.

GIST accounts for 0.1 to 3% of all gastrointestinal malignancies. It is mostly benign, with only about 30% of GISTs being malignant. It mainly occurs throughout the GI tract, with 60% of cases present in the stomach and 20% to 30% in the small intestine.

Certain factors help tell whether a GIST tumor is likely to grow and spread quickly. This includes factors such as the:

• Size of the tumor
• Location of the tumor in the GI tract
• Rate at which tumor cells divide 

This soft tissue sarcoma rarely occurs outside the GI tract, but some start outside the digestive system in nearby areas such as:

• Omentum: This is a large adipose tissue layer that lines the abdominal cavity and covers the abdominal organs.
• Mesentery: This is a membrane that attaches the intestine to the wall around the stomach area and holds it in place. 
• Peritoneum: This is a thin lining of tissue that covers the organs and lines the inside of the stomach.

Early-stage GIST may not show symptoms, especially when the tumors are small. People mostly learn they have a tumor in their GI tract when they have a test or surgery for another reason. 

When symptoms develop, they may include:

• Abdominal discomfort or pain
• Blood in your stool or vomit
• Cramping pain in the abdomen after eating
• Constipation
• Fatigue
• Losing weight 
• Loss of appetite
• Vomiting 
• Trouble swallowing
• Lump or mass in your abdomen that you can feel
• Dark-colored stools

GIST typically occurs when the KIT gene mutates, leading to uncontrolled cell growth in the digestive tract. This mutation develops during a person’s lifetime and is not inherited.

The KIT gene instructs cells to produce a protein called KIT (CD117), which promotes cell growth in the digestive tract. With gastrointestinal stromal tumors, this process goes awry, causing abnormal cells to multiply and form tumors.

In rare cases, GIST cells produce excessive amounts of another protein called PDGFRA, which can also drive abnormal cell growth.

Other causes of GIST include:

• Familial GIST syndrome: In rare cases, abnormal KIT genes get passed on from parent to child, increasing the chances of developing GIST.
• Certain tumor disorders: GIST is linked with tumor disorders, such as neurofibromatosis type 1, which causes certain cells to grow and multiply, creating tumors. 

The risk factors for developing GIST tumor may include:

• History of neurofibromatosis type 1, also known as von Recklinghausen disease
• Age 50 or older
• Rare inherited syndromes, such as Carney-Stratakis syndrome
• Family history of GIST

GISTs differ from other types of GI tract cancers as they originate from distinct cell types. Therefore, it is crucial to determine whether a GI tract tumor is a GIST, another form of cancer, or a non-cancerous condition.

Your healthcare provider may ask about your symptoms and check for growth in your abdomen. They may order the following tests for the diagnosis of a tumor:

• Imaging tests: These tests help find the location and size of your tumor. Tests may include ultrasound, CT, MRI, and PET scans. 
• Upper endoscopy: This test uses a long, thin tube called an endoscope with a light on one end. It examines the inside of the stomach and the first part of the small intestine.
• Endoscopic ultrasound: This test also uses an endoscope to look inside the GI tract with the help of an ultrasound probe on the tip of the scope. 
• Biopsy: This test involves surgically extracting a tissue sample from your tumor for lab testing. 

If a tumor is detected, the following tests may be performed to confirm GIST by analyzing the tumor cells:

• Immunohistochemistry: This laboratory test uses antibodies to detect specific antigens (markers) in a tissue sample. The antibodies are typically linked to an enzyme or fluorescent dye, which becomes activated upon binding to the antigen. This process is crucial for diagnosing GIST and distinguishing it from other types of tumors.
• Mitotic rate: This measures how quickly cancer cells are dividing and growing. By counting the number of dividing cells in a defined area of tumor tissue, it helps assess the tumor's aggressiveness, which is essential for confirming GIST and determining its behavior.

The treatment approach for GIST is not determined by the tumor’s stage but by its size, location, and whether the tumor seems to be spreading from its point of origin. 

Small GISTs that do not cause symptoms may not need treatment right away. Treatment usually starts when the tumor starts growing and spreading from the tumor site.

The treatment approach depends on the following factors:

• Resectable tumors are those tumors that can be surgically removed.
• Unresectable tumors that cannot be completely removed by surgery.
• Metastatic tumors spread to other parts of the body, while recurrent tumors are those that return after treatment. Recurrent GISTs may reappear in the gastrointestinal tract or other locations, typically in the abdomen, peritoneum, and/or liver.
• Refractory tumors are tumors that do not respond to treatment.

Surgery is the primary treatment approach used to remove the tumor cells from the affected area if the GIST has not spread and is located in a region where surgery can be safely done. 

After surgery, supportive care is often provided. The aim of supportive care is to address treatment-related side effects, monitor the recurrence of GIST tumors, and improve quality of life.

For GISTs that cannot be fully removed through surgery due to their large size or location, a multimodal approach is used to reduce the tumor as much as possible. 

• Chemotherapy: It is a targeted drug treatment that removes tumor cells from the affected area. It can be done before and after the surgery, as the first treatment approach, and if the tumor comes back.
• Clinical trial: This approach relies on the latest experimental treatments and trial options to treat GIST. 

In the United States, the five-year survival rate for GIST is 95% when the tumor is localized, meaning it is confined to the organ where it originated. For regional cases, where the tumor has spread to nearby structures, the five-year survival rate is 84%.

GIST typically does not show symptoms in the early stages. Treatment usually involves surgery and chemotherapy. When traditional treatment approaches are not effective, we offer clinical trials.

At our office in Santa Monica, we design personalized and innovative plans for treating GIST. We monitor your recovery and overall health even after you finish treatment.

To schedule a consultation, please call us at 310-552-9999 or request an appointment online.