Gastrointestinal Stromal Tumor Overview
A gastrointestinal stromal tumor (GIST) is a soft tissue sarcoma that forms in the digestive tract, usually in the stomach or small intestine. GISTs originate in interstitial cells of Cajal (ICCs), which are specialized nerve cells in the walls of the gastrointestinal (GI) system. ICCs serve as electrical pacemakers, aiding digestion by generating slow waves in the GI muscles to regulate the movement of food and fluids through the digestive tract.
Gastrointestinal stromal tumors are relatively rare, accounting for approximately 1% of GI tumors. However, GISTs tend to be aggressive and can potentially spread to other tissues and organs, which can complicate treatment.
Gastrointestinal Stromal Tumor Types
GISTs are categorized based on their site of origin in the digestive system. The most common types are gastric GISTs, which develop in the stomach, and small bowel GISTs, which develop in the small intestine. Gastrointestinal stromal tumors can also develop in the esophagus, colon and rectum.
GISTs are also classified based on their molecular characteristics and the specific gene mutations that drive their growth, which can influence their behavior and response to treatment.
Gastrointestinal Stromal Tumor Causes and Risk Factors
Scientists have linked several harmful gene mutations to GISTs. For instance, 95% of people who are diagnosed with a gastrointestinal stromal tumor have a mutation in the KIT oncogene, which produces the CD117 protein responsible for directing cells to grow and divide. The mutation causes an overproduction of ICCs.
A mutation in the platelet-derived growth factor receptor alpha (PDGFRA) gene is also associated with GISTs. Because the PDGFRA protein controls many important cellular processes, including growth, division and survival, a PDGFRA gene mutation can lead to the uncontrolled growth and division of ICCs.
Scientists do not yet fully understand the precise causes of the gene mutations associated with gastrointestinal stromal tumors. Through extensive studies, researchers have determined that the mutations can be passed from parent to child or occur spontaneously.
Regarding other risk factors, scientists do not believe lifestyle choices or environmental risk factors play a role in the development of GISTs.
Gastrointestinal Stromal Tumor Signs and Symptoms
An early-stage GIST may not cause noticeable symptoms, especially if it is small. Over time, symptoms may develop as the tumor grows and begins to press on surrounding structures.
What Does a Gastrointestinal Stromal Tumor Feel Like?
GIST symptoms that can be felt include:
- Abdominal pain
- An uncomfortable feeling of fullness in the abdomen
- Loss of appetite
- Nausea and vomiting
- A palpable mass in the abdomen
- Overwhelming fatigue
What Does a Gastrointestinal Stromal Tumor Look Like?
GIST symptoms that can be seen include:
- Abdominal bloating
- Bloody stools
- Rectal bleeding
Gastrointestinal Stromal Tumor Diagnosis
The diagnostic process for a GIST typically involves several tests and procedures, such as:
- Imaging – Computed tomography (CT) scans, magnetic resonance imaging (MRI) scans and endoscopic ultrasound may be used to help a physician visualize the tumor and evaluate its size and location.
- Blood work – A blood sample can be tested for certain proteins and other substances (tumor markers) that may indicate a GIST.
- Biopsy – A physician will remove a small sample of tumor tissue and send it to a laboratory for microscopic examination by a pathologist, who can identify cancerous cells and conclusively diagnose a GIST.
Gastrointestinal Stromal Tumor Stages
After diagnosing a GIST, the physician will assign a stage ranging from 1 to 4, with higher numbers indicating more advanced cancer. GIST stages are determined based on the size and location of the tumor, whether the cancer has spread to nearby lymph nodes and whether it has metastasized to other parts of the body.
The most widely used staging system for gastrointestinal stromal tumors is the TNM system, which was developed by the American Joint Committee on Cancer (AJCC). Cancer staging provides important information that can be used to guide treatment decisions.
Stage 1 Gastrointestinal Stromal Tumor
A stage 1 GIST is small, localized and may not produce noticeable symptoms. In many cases, the tumor is found incidentally during an imaging test performed for an unrelated reason. Treatment often involves surgery to remove the tumor, which may be all that is needed in some cases. The prognosis for stage 1 gastrointestinal stromal tumors is favorable, with a high likelihood of cure.
Stage 2 Gastrointestinal Stromal Tumor
A stage 2 GIST is larger than 5 cm in diameter but has not spread to nearby lymph nodes or metastasized to distant organs. The primary treatment is surgery to remove the tumor, which may be followed by targeted therapy. Regular follow-up care is essential to monitor for signs of recurrence. The prognosis for a stage 2 gastrointestinal stromal tumor can vary depending on specific characteristics of the cancer, but overall, it is generally favorable.
Stage 3 Gastrointestinal Stromal Tumor
A stage 3 GIST has grown into nearby tissues or organs, such as the abdominal wall or other nearby structures, but has not metastasized to distant organs. Treatment typically involves surgery to remove the tumor, which is often followed by targeted therapy to reduce the risk of recurrence. Regular monitoring and follow-up are crucial to detect and manage any recurrence early. The prognosis for a stage 3 gastrointestinal tumor can vary depending on factors such as the size, location and spread of the tumor, but it is generally less favorable than that for earlier-stage GISTs.
Stage 4 Gastrointestinal Stromal Tumor
A stage 4 GIST has metastasized to distant organs or tissues, such as the liver or abdominal lining (peritoneum), which can complicate treatment. Most patients receive a combination of surgery, targeted therapy and other treatments, such as chemotherapy or radiation therapy, to manage the symptoms and slow the progression of the cancer. Recent advances in targeted therapies have improved the outcomes and quality of life for some patients with late-stage GISTs. Regular monitoring and close collaboration with a healthcare team are essential for managing a stage 4 gastrointestinal stromal tumor.
Gastrointestinal Stromal Tumor Treatment
Common treatment options for GISTs include:
- Surgical removal, which may be appropriate for a localized, low-risk GIST
- Targeted therapy with imatinib, a tyrosine kinase inhibitor (TKI) and cancer growth blocker
- Chemotherapy
- Radiation therapy
Gastrointestinal Stromal Tumor Survival Rate
After being diagnosed with cancer, many people are interested in learning as much as they can about their condition, including the survival rate. This information can be helpful in certain situations; for instance, it serves as a useful benchmark for researchers and clinicians. However, it must always be viewed in the proper context, especially by patients.
Currently, the five-year GIST survival rate is 85%. Like all cancer survival rates, the gastrointestinal stromal tumor survival rate is intended to describe the average experience of a large group of people, each of whom is unique and has different circumstances. It is also important to keep in mind that these patients were treated several years ago before the current standard of care was available.
Additionally, hospital selection plays a key role in the survival of a cancer patient. Because gastrointestinal stromal tumors are relatively uncommon, it is essential to seek care at a high-volume cancer center. Even though the physicians at a low-volume hospital may be highly qualified, they often do not have sufficient opportunities to gain experience in diagnosing and treating rare conditions like GISTs. Significantly, when treated at a high-volume cancer center, approximately one-half of all cancer patients achieve outcomes that exceed national averages.
In sum, due to factors such as the patient’s overall health, recent advances in medical science and other dynamics, a current patient may experience a better outcome than an existing survival statistic might suggest.
Benefit From World-Class Care at TGH
Because GISTs are uncommon, specialized treatment is important. TGH’s Sarcoma Center of Excellence features a multidisciplinary team that specializes in diagnosing and treating GISTs and other types of sarcoma. Our patients collaborate closely with seasoned experts who offer the latest treatment options, including advanced targeted drug therapies that focus on specific tumor characteristics to inhibit the growth and replication of cancerous cells. In recognition of our consistently outstanding cancer outcomes, U.S. News & World Report has recognized TGH as One of the Nation's Best Hospitals for Cancer Care for 2024-25.
If you would like to learn more about gastrointestinal stromal tumors, contact Tampa General Hospital at (813) 844-7585 to request an appointment with an expert in our Cancer Institute in Tampa, FL.