Gastrointestinal Stromal Tumors (GIST) are rare, accounting for less than 1% of primary tumors of the gastrointestinal (GI) tract. A GIST tumor can occur throughout the GI tract, with 60% occurring in the stomach, 30% in the small intestine, 5% in the colon and rectum, and 5% in the esophagus. GIST tumors are thought to arise from the interstitial cells of Cajal that are normally part of the autonomic nervous system. They serve a pacemaker function in controlling bowel motility.
Approximately 70 to 80% of GISTs are benign and can range in size from 1cm up to 30cm in diameter. Malignancy is characterized by local invasion and metastasis to the liver, omentum and abdominal cavity or peritoneum.
What are the symptoms of Gastrointestinal Stromal Tumors (GIST)?
GIST tumors present in many ways with 3% diagnosed incidentally. Small tumors may be asymptomatic and can grow to a large size before producing symptoms. This may be because GISTs grow by displacing adjacent organs and structures rather than invading them. Symptoms include vomiting, abdominal pain, distension, change in bowel habits and, less frequently, obstruction and bleeding.
How is a Gastrointestinal Stromal Tumors (GIST) diagnosed?
Various investigations may be used in the diagnosis of a GIST. Diagnostic tests may include endoscopy, CAT scan of the abdomen/pelvis, Magnetic Resonance Imaging (MRI) and Positron Emission Test (PET). The purpose of radiologic imaging is to locate the tumor, evaluate for signs of invasion and detect metastasis.
How is a Gastrointestinal Stromal Tumor (GIST) treated?
Surgical resection of the tumor is the mainstay of therapy for non-metastatic GIST and involves removal of the affected segment of bowel. This can be accomplished with a traditional, open approach or with some of the newer minimally invasive surgeries such as laparoscopic and robotic techniques. The operation is performed on an inpatient basis and patients typically are in the hospital for four days after surgery.
Until recently, GISTs were notorious for being resistant to chemotherapy, with a success rate of less than 5%. Recently, Gleevec a chemotherapeutic treatment for leukemia, has shown significant improvement in treatment, leading to 40 to70% response rate in patients with inoperable tumor or metastasis.