Gastrointestinal stromal tumor
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A gastrointestinal stromal tumor (GIST) is a rare disease where a tumor forms in the gastrointestinal (GI) or digestive tract. This occurs when the special nerve cells in the wall of the GI tract develop abnormally and quickly spreads in the body. These special nerve cells function in the process that moves food through the body.
GIST can start anywhere near or in the GI tract, but most begin in the small intestine, and more than half begin in the stomach.
GISTs can range in size from small and benign, to large and malignant. While some individuals may not experience any symptoms, others may feel ill or experience pain or bleeding.
Symptoms
The symptoms associated with GISTs can vary depending on its size and location in the abdomen or other parts of the body. Sometimes, a small GIST may go unnoticed and is only discovered after tests for another illness. If a GIST develops, the symptoms may include:
- Severe abdominal pain or abdominal discomfort
- Blood in the stool or vomit
- Unusual mass in the abdomen
- Abdominal pain that worsens after eating
- Tiredness
- Nausea and Vomiting
- Loss of appetite
- Feeling satisfied after a small meal
- Weight loss
- Difficulty swallowing
GIST is a rare condition. Although it can happen to everyone, it is uncommon to people under 40 years of age. The majority of GISTs have an unknown cause. In very rare cases, it can be hereditary and can occasionally be seen in multiple family members.
Cause
The mutation of the cells lining of the digestive tract causes uncontrolled duplication resulting in forming a mass of cells called as GIST. This tumor then begins to invade and destroy the normal cells. Most GIST present mutation in the KIT oncogene result in abnormal cell division and tumor growth.
Risk factors
There are few potential risk factors that increases one’s risk of getting GIST:
- Age: People in their 50s or older have higher risk of developing tumors compared to people 40 years old and younger.
- Familial GIST syndrome: The genetic material inherited from a person’s parents is stored in genes found in cells. People who have inherited a gene mutation (change) are more likely to develop GIST. This mutation is typically caused by a KIT gene abnormality.
- Neurofibromatosis type 1 (von Recklinghausen disease): This is a genetic condition that affect mainly skin and nerve cells in the skin, brain, eyes and other part of the body. It occurs due to an alteration or defect in the NFI gene. This can occur before birth or inherited.
- Carney-Stratakis syndrome: Patients with this rare genetic condition have a higher risk of GIST and other nerve tumors.
It is recommended to seek medical advice if any of these or other comparable conditions are present in the family. Although GIST can be hereditary, majority of the cases still arise from spontaneous cellular alterations.
Diagnosis
The diagnosis of GIST often starts with a physical exam and assessment of medical history. If GIST is suspected, severe tests may be required:
- Imaging tests: Ultrasound, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) scans provide images of the body to determine whether a suspicious spot may be a tumor, and the extent of its spread and assess effectivity of treatment.
- Upper endoscopy: known as esophagogastroduodenoscopy or EGD, an investigation consisting of a flexible thin tube connected to a tiny camera which will be inserted into a patient’s mouth, passing through the throat to evaluate the esophagus, stomach, and the first part of small intestine to evaluate for any abnormal sign.
- Endoscopic ultrasound (EUS): A tiny tube with camera is inserted into the throat down to the stomach and then a special ultrasound is utilized to view images of its internal structure. EUS can take photos of the tumor and calculates the size using sound waves.
- Fine-needle aspiration biopsy: Also known as an endoscopic ultrasound-guided fine needle aspiration (EUS-FNA), uses hollow needles to collect small amounts of tissue for lab testing. Rarely, the doctor might use an imaging test like a CT scan to guide the placement of a needle through the skin and into the tumor. In some cases, a surgery may be recommended if the results are unclear because the needle cannot reach enough cells.
- Laboratory tests on biopsies: A pathologist may be able to determine if a tumor is most likely a GIST after examining the tumor sample cells under a microscope. If they are potentially cancerous, the doctor may require more tests such as immunohistochemistry and molecular genetic testing for more information about the cells and for creating an effective treatment plan.
Treatment
There are different types of treatments for GIST according to the size and location of the GIST, test results and overall health condition. Common treatments are targeted drug therapy and surgery.
In some cases, “watchful waiting” may be suggested. A patient’s condition is carefully monitored through scheduled appointments one or twice a year. No treatment is given until new or different indications or symptoms develop. This is common in very small tumors that are not growing quickly and is considered low risk.
Surgery
Surgery as a treatment for GIST is often recommended on tumors that are localized or has not spread. The type of surgery is determined by the size and location of the tumor.
Small GISTs can be removed laparoscopically, a minimally invasive procedure that will require making a many small incisions in the abdomen to remove the tumor. The surgeon uses a laparoscope to visualize the internal organs. It is put into one of the small incisions that are created on the abdominal wall. This procedure allows shorter recovery time for patients.
For larger GISTs, especially if it affects neighboring organs, surgery may be not recommended right away. The initial course of treatment is to proceed with neoadjuvant therapy or targeted drug therapy to make the tumor shrink, making surgery to remove it easier.
Targeted drug therapy
Targeted drugs or precision medications are considered beneficial in treating GISTs. Certain proteins that aid in cell division and growth in gastrointestinal stromal tumor (GIST) cells can be targeted by these medications. These aim to block the tyrosine kinase enzyme, which promotes the growth of cancer cells, in GISTs. Compared to chemotherapy or radiation therapy, targeted therapies typically have a lower impact on healthy cells.
Imatinib, an oral pill, is often prescribed as the first course of targeted drug therapy for GIST, especially to:
- Reduce the risk of recurrence of cancer after surgery
- Reduce the size of the tumor for easier surgery
- Treat advance GISTs that has spread to other areas
- Manage recurring GISTs
Patients that became resistant to imatinib may be prescribed with other targeted drugs such as sunitinib, regorafenib and ripretinib. New medications are expected to become available in the future.
Although surgery or targeted drug therapy can remove or eliminate the GIST, there is still a chance that it may come back after the treatment. Doctors strongly suggest having a follow-up care to monitor the health condition and manage side effects of treatment, if there is any.
