Gastrointestinal stromal tumors (GISTs) are tumors that form in the digestive tract — most often the stomach or upper part of the small intestine. GISTs usually begins in cells in the wall of the stomach, intestines, or rectum.
- Small intestine
GISTs can be cancerous (malignant) or noncancerous (benign). Malignant GISTs often spread to the liver. GIST treatment most often involves surgery and targeted therapy drugs.
- Neoplasm of the stomach
- Feeding difficulties in infancy
- Gastrointestinal hemorrhage
- Intestinal obstruction
- Nausea and vomiting
- Abnormality of the liver
- Esophageal neoplasm
- Irregular hyperpigmentation
- Neoplasm of the colon
- Neoplasm of the rectum
- Neoplasm of the small intestine
- Skin rash
- Autosomal dominant inheritance
- Gastrointestinal stroma tumor
- Hyperpigmentation of the skin
- Large hands
Most GISTs are sporadic (not inherited) and have no clear cause. In rare cases, though, GISTs have been found in several members of the same family. These family members inherited a gene mutation that can lead to GISTs.
The cause is not exactly understood. However,, it is known that the cancer cells of most patients with GIST have a change in an oncogene called c-kit. The c-kit gene is found in all cells of the body. It leads to the formation of a protein called KIT. This protein causes the cell to grow and divide. Usually the c-kit gene is inactive. It is only activated if there is a need for more interstitial cells of Cajal (ICCs). In most GISTs the c-kit gene is mutated and is always active.
There is not yet a know way to prevent GISTs. In some rare cases the disease has been diagnosed in members of the same family, but this is not a factor that can be controlled.
Screening refers to tests and exams used to find a disease such as cancer in people who do not have any symptoms. The American Cancer Society has recommendations for screening tests to find several types of cancer as early as possible. But for rare tumors like GISTs, no effective screening tests have been found, and routine testing of people without any symptoms is not recommended.
GISTs may be found early by chance. Sometimes they are seen on an exam for another problem, such as during colonoscopy to look for colon cancer. Rarely, a GIST may be seen when an imaging test, such as a computed tomography scan (CT scan) or barium study, is performed for another reason.
For GISTs, factors such as the size of the tumor, its grade, and whether it has already shown signs of spread in the abdomen can be helpful in predicting how fast the cancer will grow and how likely it is to come back after treatment. Before the staging system was developed, doctors often used these factors to help predict the outcome of patients with GIST, as well as to select the best treatment.
The size of the tumor can give some indication of prognosis (outlook). Smaller tumors (generally those less than 2 inches across) tend to be less likely to spread and have better outcomes than larger ones. The best outlook is for tumors smaller than 1 inch.
Another factor in prognosis is the tumor's histologic grade - its tendency to grow and spread more rapidly based on how the cells look under the microscope. For GISTs, this is done by finding out how many dividing cells, or mitoses, there are. The pathologist looks at many different areas (or fields) of a tumor sample under the microscope and counts the actual number of dividing cells. By doing these counts, the doctor comes up with a number called mitoses per high-powered field. This number will help predict whether the GIST is most likely to be a cancer or a benign tumor.
For patients with primary, localized gastrointestinal stromal tumors, surgery with complete excision is the treatment of choice. However, surgery has limited efficacy in the treatment of recurrent and metastatic gastrointestinal stromal tumors. These tumors are also resistant to both chemotherapy and radiotherapy. In the pre-imatinib era, the 5-year survival rate after the surgical resection of gastrointestinal stromal tumors was only 43%–80% as there was really no efficient method to cure the disease. The addition of imatinib as part of the treatment of unresectable or recurrent gastrointestinal stromal tumors has improved the management of this condition and resulted in improved patient survival.
- Imatinib mesylate (Gleevec) - FDA-approved indication: Treatment of patients with Kit (CD117) positive unresectable and/or metastatic malignant gastrointestinal stromal tumors (GIST)
- Regorafenib (Stivarga) - FDA-approved indication: Treatment of patients with locally advanced, unresectable or metastatic gastrointestinal stromal tumor (GIST) who have been previously treated with imatinib mesylate and sunitinib malate.
- Pazopanib (Votrient) - FDA-approved indication: Advanced soft tissue sarcoma (STS) who have received prior chemotherapy.