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GIST

Colorectal Cancer Treatment

What Are Gastrointestinal Stromal Tumors (GIST)?

Gastrointestinal stromal tumors (GISTs) are rare tumors that start in special cells found in the wall of the GI tract, called the interstitial cells of Cajal (ICCs). ICCs are part of the autonomic nervous system, and coordinate the automatic movements of the GI tract. ICCs are sometimes called the “pacemakers” of the GI tract because they send signals to the muscles of the digestive system, telling them to move food and liquid through the GI tract.

GISTs may occur anywhere along the length of the digestive tract from the esophagus to the anus.

GIST is slightly more common in men. Although GISTs are most often diagnosed in people 50 years of age or older, they can occur in any age group. GIST appears to occur with increased frequency in patients with a history of neurofibromatosis (NF1 disease).

Approximately 50-70% of all GISTs develop in the stomach, while around 20-30% will arise in the small intestine. The rest arise in the esophagus, colon, and rectum.

Most people who develop GIST have a mutation in a gene called c-kit, but researchers are not certain how the mutation causes the cancer and the cancer does not always manifest in the same way.

Symptoms of Gastrointestinal Stromal Tumors (GIST)

People with early stage GIST often do not have any symptoms of the disease. Most GISTs are diagnosed after a person develops symptoms. These may include:

  • Abdominal discomfort or pain
  • Vomiting
  • Blood in stools or vomit
  • Fatigue due to anemia (low blood counts)
  • Feeling full after eating only a small amount (early satiety)
  • Loss of appetite
These symptoms may be the result of GIST or of other less serious causes. A person with these symptoms should discuss them with their doctor.

Why Gastrointestinal Stromal Tumors Develop

The way in which GIST grows, or the route the tumor takes when it spreads through the body, is called its pathophysiology.

Scientists are beginning to unravel some of the processes that go on inside cells that cause them to develop into GISTs. Normally these cells, like other cells in the body, grow and divide in a controlled fashion. But sometimes things can go wrong, allowing these cells to grow out of control and ultimately become cancerous.

Scientists have discovered that cells may grow in an uncontrolled manner as the result of an abnormality in their DNA. In GIST, a specific mutation causes a cellular enzyme known as KIT to be switched “on” all the time. KIT is an enzyme (called a “tyrosine kinase”) responsible for sending growth and survival signals inside the cell. If it is ON, the cell stays alive and grows or proliferates. The overactive, uncontrolled mutant KIT enzyme triggers the runaway growth of GIST tumor cells. This insight into the way GISTs develop has already helped to identify new treatments for this sarcoma.

 

Risk factors for GIST

  • Neurofibromatosis
    The most substantial risk factor for GIST is the presence of neurofibromatosis.
  • Family History
    There are rare instances of familial GIST where several family members have the condition.

Diagnosing GIST

If a person feels a lump or experiences symptoms that may indicate the presence of a GIST, he or she should discuss them with a doctor. The doctor will take a detailed history of the patient and ask questions about the symptoms.

  • Scans and tests
  • Biopsy

GIST can come in many forms. It can arise from different kinds of cells (e.g., gland cells, squamous cells) and it can be either benign or malignant.

Your doctor, along with an expert pathologist, will evaluate your symptoms, how far the cancer has spread, and the precise characteristics of the cancer cells to help determine whether your GIST is benign or malignant, and what stage the cancer is.

Treatment Options for Gastrointestinal Stromal Tumors (GIST)

Chemotherapy
The use of anticancer drugs to shrink or kill cancerous cells and reduce cancer spreading to other parts of the body.

Chemotherapy/RT
A regimen of radiation therapy and low-dose chemotherapy given concurrently.

Because there is a chance that malignant tumors can recur or come back after surgery, chemotherapy or radiation is used with many types of cancer. This is called adjuvant therapy. However, in the case of GIST, using either chemotherapy or radiation after surgery has not been shown to work in preventing the tumor from coming back. For this reason researchers have sought new effective therapies for GIST.

Radiation therapy
The use of high-energy radiation to kill or shrink cancer cells, tumors, and non-cancerous diseases.

Surgery
Until recently, the only treatment for GIST had been surgery. The goal of surgery is to remove the tumor completely. However, surgery alone for larger GISTs, or for GISTs that have spread, yielded disappointing results.