Gastrointestinal stromal tumor (GIST) is a rare type of soft tissue sarcoma of the gastrointestinal (GI) tract. In most of the cases, small GISTs (<2 cm) are harmless benign tumors; however, larger GISTs (≥2 cm) are often malignant and can be life-threatening, if left untreated.
What are the Risk Factors?
Till date, very little is known about the risk factors related to GISTs. Having a family history of the disease (parent carrying mutations in certain genes) increases the chance of developing familial GISTs. However, this type of cancer is hereditary only rarely.
Since GISTs are known to mostly affect people in older age (greater than 40 years), physiological changes associated with aging may have some role in the pathogenesis of GISTs.
In some cases, GISTs may be part of a genetic syndrome, which can be a set of coexisting conditions caused by genetic mutations. Genetic syndromes which are associated with GIST include:
Primary familial GIST syndrome – People with this type of inherited condition are at higher risk of developing GISTs. It is caused by mutations in KIT gene which are transmitted from a parent to the offspring. Moreover, mutations in PDGFRA gene are also known to be associated with 5 to 10% of the cases with sporadic (non-inherited) GISTs.
Neurofibromatosis type 1 (NF1) – this syndrome is caused by mutations in NF1 gene, and people with this disorder have higher risk of developing GISTs. Typical signs and symptoms of this disease are benign tumors in nerves throughout the body and brown spots on the skin.
Carney-Stratakis syndrome – this inherited syndrome, which is caused by mutations in one of the succinate dehydrogenase genes, increases the chances of developing GISTs. People with this syndrome are more likely to develop GISTs in their teens or 20s.
Signs and Symptoms of GISTs
The signs and symptoms of GISTs may also be associated with other coexisting conditions. Thus, a thorough medical examination is needed to understand the underlying conditions.
Small GISTs are generally asymptomatic. The most frequent sign of larger GISTs is the presence of blood in the stool and/or vomit. Blood in the stool or vomit is either bright red or very dark in color. Bleeding from the tumors situated in the esophagus or stomach is the main reason of vomiting blood; whereas, bleeding from the tumors located in the stomach or small intestine is associated with blood loss through the stool (black and tarry stool). In contrast, bleeding from the tumors situated into the large intestine is more likely to produce red color stool with visible blood.
Other symptoms of GIST include:
- Severe abdominal pain – a fast-growing tumor can sometimes block the passage of food through the GI tract. Such obstruction can lead to severe abdominal pain and vomiting. In addition, fragile GISTs can also rupture easily to form holes in the GI tract, which can also cause severe abdominal pain.
- Swelling in the abdomen – mass formation in the GI tract results in swelling in the abdomen.
- Problem swallowing – tumors formed in the esophagus often cause difficulty in swallowing.
- Anemia – slow-bleeding tumors decrease the red blood cell count, which results in anemia.
- Fatigue – chronic anemia may cause weakness and lethargy
- Nausea and vomiting
- Loss of appetite
- Feeling full even after having a small meal
- Weight loss
Treatment of GIST
Treatment of GIST mainly depends on the size and position of the tumor. Surgery is the primary option for treating large GISTs. However, surgery is generally avoided if the tumor is very large in size, or involves many organs or tissues. In many cases, minimally invasive surgeries such as laparoscopy, are also performed to remove GISTs.
Traditional chemotherapy and radiotherapy do not work on GISTs. However, targeted drugs that effectively inhibit the cancer cell growth and metastasis are very helpful in treating GISTs. For instance, the most effective growth inhibitors which are used to treat GIST include kinase inhibitors. These drugs are particularly useful when surgery is not possible, as well as to prevent cancer recurrence after surgery.