Gastrointestinal Stromal Tumor (GIST)

A GIST is an uncommon type of tumor that develops in the connective tissues of the gastrointestinal (GI) tract. A key part of the digestive system, the GI tract consists of the esophagus, stomach, small intestine, large intestine, rectum and anus. Together, these organs form a pathway for swallowed food to travel through the body. The primary function of the GI tract is to break down food into nutrients that can be absorbed by the body. The resulting waste products are then eliminated through the anus.

Although GISTs can form anywhere along the GI tract, they are most common in the stomach and small intestine. Not all GISTs are cancerous, and some grow slowly without spreading. Nevertheless, an accurate diagnosis is essential to ensure the best possible outcome and quality of life.

What are the causes and risk factors for gastrointestinal stromal tumors?

The exact cause of most GISTs is unclear. However, many cases are linked to a harmful change in the KIT or PDGFRA gene. These genes produce proteins that regulate cell growth and survival in the digestive tract. When a KIT or PDGFRA gene mutation occurs, the proteins produced may become overactive, causing the cells to multiply uncontrollably and form a tumor.

While most gastrointestinal stromal tumors occur randomly, a few factors may increase the risk. These include:

• Advanced age – Most GISTs occur in adults older than 40.
• Genetics – Certain rare inherited conditions, such as Carney-Stratakis syndrome and neurofibromatosis type 1 (NF1), as well as a family history of GISTs, can increase the risk of developing gastrointestinal stromal tumors.

GISTs affect men and women at similar rates, and there are no known lifestyle-related causes.

Are gastrointestinal stromal tumors preventable?

Currently, there are no proven ways to prevent GISTs. Because many cases are linked to a genetic mutation that occurs sporadically, routine cancer prevention methods—such as consuming a nutritious diet and exercising regularly—do not significantly reduce the risk. However, early detection and specialized care can help improve the outcome.

What are the signs and symptoms of a gastrointestinal stromal tumor?

The symptoms of a gastrointestinal stromal tumor can vary based on its size and location. Many small GISTs do not cause noticeable symptoms and are discovered incidentally during an imaging test or surgery performed for another reason.

What are the early warning signs of a gastrointestinal stromal tumor?

Early warning signs of a GIST may include:

• Mild abdominal discomfort or pain
• Fatigue or general weakness
• A feeling of fullness after a small meal (early satiety)

What are the most common symptoms of a gastrointestinal stromal tumor?

Common symptoms of a GIST include:

• Anemia from internal bleeding
• Blood in the stool or vomit (which may appear black or tarry)
• Nausea or vomiting
• A noticeable lump or mass in the abdomen
• Unexplained weight loss

What are the symptoms of an advanced gastrointestinal stromal tumor that has spread?

If a GIST grows or spreads to another part of the body, symptoms may become more severe, such as:

• Persistent abdominal pain or swelling
• Shortness of breath or fatigue due to blood loss or anemia
• Yellowing of the skin or eyes (jaundice), if the liver is affected

How are gastrointestinal stromal tumors diagnosed?

Because GISTs can resemble other types of digestive tumors, an accurate diagnosis is crucial to ensure effective treatment. To confirm the presence and type of a tumor, the physician may use a combination of clinical evaluation, laboratory tests, imaging studies and minimally invasive procedures.

What laboratory tests are used to diagnose gastrointestinal stromal tumors?

Lab tests that may be used to diagnose a GIST include:

• Blood work – To check for anemia and other abnormalities
• Molecular testing – Can detect mutations in the KIT and PDGFRA genes to guide treatment planning

What imaging tests are used to diagnose gastrointestinal stromal tumors?

Imaging tests commonly used to diagnose GISTs include computed tomography (CT) and magnetic resonance imaging (MRI) scans, which can provide detailed images of the abdominal structures to help the physician assess the size and spread of the tumor. In some cases, the physician may order a positron emission tomography (PET) scan to evaluate the activity of the tumor.

What procedures are used to diagnose gastrointestinal stromal tumors?

To diagnose a GIST, the physician may perform a minimally invasive procedure, such as:

• Upper endoscopy – This test uses a long, thin tube (endoscope) with a miniature camera and light attached to the end. After inserting the endoscope into the mouth and guiding it down the throat, the physician can view the inside of the esophagus, stomach and the upper segment of the small intestine.
• Endoscopic ultrasound (EUS) – This test uses an endoscope with an ultrasound probe attached to the tip. Using the probe, the physician can generate high-frequency sound waves to create detailed, real-time images of the tumor.
• Fine-needle aspiration (FNA) biopsy – This test uses an endoscope with a thin, hollow needle attached to the tip. After locating the tumor, the physician will use the needle to collect a small tissue sample for microscopic examination by a pathologist, who can identify cancerous cells.
• Surgical biopsy – If an FNA biopsy does not provide sufficient cells for testing or the result is unclear, a surgical procedure may be performed to collect a larger tissue sample.

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How are gastrointestinal stromal tumors treated?

GIST treatment can vary based on the size, location and stage of the tumor. Many patients benefit from a combination of surgery and targeted therapy, although immediate treatment is not always necessary. If the GIST is small and not causing symptoms, the physician may suggest a wait-and-watch approach. Through periodic imaging scans, the physician can monitor the development of the tumor, allowing the patient to safely delay treatment until it becomes necessary.

While traditional chemotherapy and radiation therapy are not usually effective against gastrointestinal stromal tumors, these treatments may be used in select cases if other approaches are not suitable. Additionally, immunotherapy may be an option through a clinical trial. This novel treatment approach can help the body’s immune system recognize and destroy cancer cells more effectively.

How is surgery used to treat gastrointestinal stromal tumors?

Surgery is the primary treatment for most localized GISTs. The goal is to remove the tumor completely while preserving as much healthy tissue as possible. In many cases, the surgeon can perform a minimally invasive procedure, accessing and removing the GIST through small incisions in the abdomen. This approach can eliminate the need for traditional surgery, which typically involves a large incision and prolonged recovery.

If the GIST is large or has invaded nearby structures, treatment may begin with targeted therapy to shrink the tumor, possibly followed by surgery at a later date.

How is targeted therapy used to treat gastrointestinal stromal tumors?

Targeted therapy uses specialized medications designed to block specific chemicals found in the cancer cells, ultimately causing those cells to die. For GISTs, the target is usually tyrosine kinase, an enzyme that promotes cancer cell growth.

Targeted therapy for a gastrointestinal stromal tumor may begin with imatinib (Gleevec®), which can be given:

• After surgery to lower the risk of cancer recurrence
• Before surgery to shrink the tumor and make it easier to remove
• As the first-line treatment if the cancer has spread to other parts of the body
• If the GIST comes back after initial treatment

Other targeted therapy medications might be considered if imatinib is ineffective or stops working. Targeted therapy is an active area of cancer research, and new medications are likely to become available in the future.

What are some frequently asked questions (FAQs) about gastrointestinal stromal tumors?

Receiving a GIST diagnosis can raise many questions about what to expect moving forward. For instance, many patients want to know whether this rare condition is cancerous, how it develops and how it can be treated. With an understanding of the basics, a patient can make more informed decisions about their care and feel more confident throughout their treatment journey.

Here are answers to some of the most frequently asked questions about GISTs.

Is a gastrointestinal stromal tumor cancerous?

Not every GIST is cancerous. Some tumors are benign and grow slowly, while others can advance and spread to other tissues and organs. Through genetic and pathological testing, the physician can evaluate the aggressiveness of the GIST and recommend the best treatment approach.

How serious is a GIST diagnosis?

The seriousness of a gastrointestinal stromal tumor can vary depending on its stage and whether it has spread. A small, localized tumor may be completely removed with surgery, while a large or metastatic GIST may require additional treatment, such as targeted therapy.

Can a gastrointestinal tumor come back after treatment?

Some GISTs can recur after surgery, especially if the tumor was not completely removed. Once treatment is complete, ongoing monitoring through imaging studies and follow-up visits will be essential to reduce the risk of recurrence.

Are clinical trials available for gastrointestinal stromal tumor treatment?

Yes. GIST research is ongoing, and promising new targeted therapies and drug combinations—designed specifically for gastrointestinal stromal tumors—are currently being evaluated in clinical trials.

How often will I need follow-up care after GIST treatment?

After completing treatment, most patients undergo imaging studies—such as CT or MRI scans—every three to six months for the first few years. These follow-up tests can help the physician monitor for early signs of recurrence and address any lingering side effects of treatment. Over time, the frequency of the appointments may decrease based on the patient’s risk level and progress.

Benefit from world-class care at Moffitt Cancer Center

Moffitt is home to a comprehensive program that incorporates a full range of diagnostics, treatment options, clinical research trials and support services for patients with GISTs. Taking a highly collaborative approach to cancer care, we address all of our patients’ healthcare needs and concerns in a single, convenient location.

The multispecialty GIST team at Moffitt includes members of our Sarcoma Program and Gastrointestinal Oncology Program, as well as experts from many other disciplines, such as surgical oncologists, medical oncologists, radiation oncologists, interventional radiologists, endoscopy specialists, pathologists, supportive care specialists and nurses. These knowledgeable and experienced specialists work closely together to plan and carry out an individualized treatment plan for each patient.

Moffitt is firmly positioned at the forefront of GIST research. By offering our patients access to promising new treatment opportunities through our robust portfolio of clinical trials, we have distinguished ourselves as a global leader in the fight against gastrointestinal stromal tumors. In many cases, our patients are among the first to benefit from advanced therapies that are not yet offered anywhere else.

If you would like to request an appointment with a GIST specialist at Moffitt, call 1-888-663-3488 or complete our new patient registration form online. We do not require referrals.

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