Gastrointestinal stromal tumors (GIST) are a key in of soft tissue sarcoma.
The diagnosis can be challenging, but is most often made with an endoscopic ultrasound.
It’s currently believed that GISTs arise from cells called interstitial cells of Cajal (ICCs).
Jose Luis Pelaez / The Image Bank / Getty Images
That said, most very small GISTs that begin in the stomach behave like benign tumors.
When they do spread, the most common sites are the lungs and bones.
It’s thought that roughly 5,000 cases are diagnosed in the United States each year.
BRCA genes are examples of tumor suppressor genes.
Tumor suppressor genes may also be affected in some people with GIST.
These are in contrast to hereditary or germline mutations that are associated with hereditary cancers.
When a cancer is related to a hereditary mutation, it is referred to as ahereditary cancer.
In contrast, when a cancer is due to an acquired gene mutation, it is considered asporadic cancer.
KIT and PDGFRA gene mutations are associated with both hereditary and sporadic GISTs.
Genetic Syndromes and GIST
A number of different genetic syndromes are associated with GIST.
They may be found incidentally or after investigating the symptoms they can cause.
The average size at the time of diagnosis is 5 cm (roughly 2.5 inches) in diameter.
Imaging Tests
Imaging tests are often done initially.
The disadvantage of imaging tests is that a biopsy is not usually performed.
A PET scan may, however, be helpful in staging.
Capsule endoscopyis a procedure in which a capsule containing a small camera is swallowed.
The camera passes normally with a bowel movement and does not need to be retrieved.
A disadvantage of capsule endoscopy is that a biopsy cannot be done with the procedure.
this procedure involves inserting two endoscopy tubes, with one inside of the other.
Mitotic cells are cells that are noted to be in the active stage of cell division.
It’s currently recommended that everyone with a GIST be tested for KIT and PDGFRA mutations.
If negative, testing for BRAF, SDH, and NF1 should be undertaken.
These tumors may also harbor gene mutations that may guide treatment.
Tumors that are positive for both CD117 and DOG1 have a 97% chance of being a GIST.
CD117 isn’t specific for GIST, and may be positive with some other types of sarcoma.
Other immunostaining techniques are helpful in some cases.
In one study, mutations were found in 82% of tumors that tested negative for KIT and PDGFRA.
Several clinical trials are also in progress.
Even if some tumor is present on the margins, re-surgery is not usually done.
It’s very important to have a surgeon who is experienced in GIST surgeries.
Adjuvant therapyrefers to the use of targeted therapyaftersurgery to reduce the risk of recurrence.
Neoadjuvant therapyrefers to the use of targeted therapy (Gleevec)beforesurgery to reduce the size of a tumor.
This can sometimes result in a much less invasive surgery.
Other times, a tumor that is previously inoperable may become operable after a period of using targeted therapy.
In this setting, the targeted therapy is usually used for around 2 years before surgery is performed.
They do not, however, cure a cancer, and these tumors often recur once treatment is stopped.
For people with unresectable or metastatic GIST, targeted therapy is usually the treatment of choice.
It is also often recommended as adjuvant or neoadjuvant therapy.
It may also be started after surgery in cancers that have a significant risk of returning.
The most common side effects are rashes, diarrhea, abdominal pain, and muscle aches and pains.
Exceptions: Some GISTs are less likely or unlikely to respond to Gleevec.
Stirvarga (Regorafenib)
Stivarga is usually recommended third line, when both Gleevec and Sutent stop working.
When a tumor is controlled on Gleevec, many people wonder how long the medication should be continued.
That said, they tend to grow more slowly.
BRAF
GISTs that harborBRAF mutationsmay respond to the currently available BRAF inhibitors used for melanoma and other cancers.
NTRK Gene Fusion
Roughly 1% of GISTs may harbor a neutrophil receptor kinase (NTRK) gene fusion.
With distant recurrence, a tumor is then treated as a metastatic tumor, usually with targeted therapy.
When tumors progress, the next available targeted therapy is often used.
With a distant progression (metastasis), sometimes local treatment is used in addition to the targeted therapy.
When this occurs, local treatment of the metastasis can sometimes result in control of the tumor.
Ablation (radiofrequency ablation) or arterial embolization procedures are most often used.
With many types of cancer, a treatment is discontinued when the cancer progresses while on that treatment.
Clinical Trials
With many GISTs, aclinical trialmay be a good option.
KIT and PDGFRA positive tumors seem to have a similar prognosis.
But new treatments have been adopted since that time.
Fortunately, there are now many treatment options available for most of these tumors.
Support
The importance of support can’t be overstated when you are coping with cancer.
The internet is a great way to connect with others when you are facing an uncommon cancer.
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