What is GIST?
- Carcinomas start in the cells that cover the lining of the skin and organs (epithelial cells). Most stomach and colon cancers are carcinomas. Skin cancer is another type of carcinoma.
- Soft tissue sarcomas start in the cells of the connective tissues like cartilage, fat, nerves, and muscle.
More specifically, GIST starts in nervous system cells in the wall of the GI tract -- called interstitial cells of Cajal (ICCs). These cells send signals to the muscles in the digestive system to contract to move food and liquid through the system.
What causes GIST?
GIST is caused by a genetic mutation, an error in the normal order of genes. In most cases, the mutation is to a gene that directs the cells to make a protein (called KIT or CD117) that causes the cells to grow and divide. In this case, the gene mutation causes the ICC cells to grow and divide in an uncontrolled manner, leading to a tumor.
Risk factors for GIST include certain inherited gene mutations.
What is mutation testing?
Mutation testing may be done on the cancer cells to identify the exact genetic mutation that exists. This helps doctors understand how the cancer may behave and aid in guiding treatment.
At this time, mutation testing is recommended for everyone with GIST. Testing for the Kit mutation will be positive in 87% of cases of GIST. Testing for the PDGFRA genetic mutation will be positive in 4% of GIST cases.
How is this cancer staged?
Doctors use staging to determine the extent of a malignancy. These three factors determine staging:
- The size and location of the tumor
- Whether or not cancer has spread to lymph nodes or other organs
- How fast the cells are growing
The chart below shows how letters and numbers are used to identify your cancer stage. This information helps guide your treatment and prognosis.
|Letter||What it refers to|
|T||Size of the tumor (1 - 4)|
|N||Indicates whether it has spread to nearby lymph nodes (rare for GIST) most GISTS will be “N0” (zero).|
|M||Indicates whether the cancer has spread to nearby organs. (0 or 1)|
|Mitotic rate||How fast the cancer is growing (low or high)|
Do I need to see a specialist?
Because GIST is rare and can be unpredictable, choosing the correct doctor is an important decision. There are a limited number of doctors and medical centers experienced in treating GIST. Talk to your doctor about finding a doctor who is skilled in GIST treatment.
In most cases, a team of experts is assembled to treat you. These medical experts include:
- A cancer specialist (oncologist)
- A doctor specializing in treatment of the GI tract (gastroenterologist)
- A surgeon
Take an active role in your treatment and work closely with the medical team. The following activities can help you take control of your treatment:
- Asking questions
- Doing research
- Getting second or third opinions if necessary
- Finding support from others who have GIST
- Locating GIST support groups.
- Connecting with others online who have GIST
What are my treatment options?
The primary treatment of GIST is surgery to remove the tumor, if possible (85% of the time). Surgery is recommended for any tumor over 2 cm in size. The actual surgical procedure will differ depending on where the tumor is located. It may be done using laparoscopic or open surgical techniques. The surgeon will remove the tumor and a small area of tissue surrounding the tumor, taking care not to rupture the tumor, which would cause cancer cells to spill into the abdomen.
In some cases, doctors will remove a suspicious-looking tumor even before any diagnosis is made. You may not have been diagnosed with GIST until after surgery.
When surgery cannot be done to remove a GIST, or when the cancer has spread to other organs, the medication imatinib (Gleevec) may be prescribed. Gleevec targets the specific cells responsible for GIST (Kit). Imatinib will either shrink the tumor, or stop its growth in the majority of cases. If your cancer has spread, the drug will not cure the cancer, but it may improve the quality and length of life.
Imatinib (Gleevec) may also be taken for up to three years after a tumor is removed, to try to keep the cancer from returning. However, the drug may stop working with time. In these instances, the dose of imatinib may need to be increased or a different drug prescribed.
If you can’t take Gleevec or become resistant to it over time, another drug called sunitinib (Sutent) is available. The drug regorafenib (Stivarga) is used to treat patients who have tumors that cannot be surgically removed and no longer respond to Gleevec or Sutent.
Research has found that chemotherapy and radiation are not effective in the treatment of GIST.
What is the prognosis for someone diagnosed with GIST?
It’s difficult to predict if GIST cancer will return. Based on tumor size and how fast it is growing, the tumor will be categorized as low, intermediate, or high risk. The location of the primary tumor also plays a role in the risk of tumor recurrence. Tumors in the stomach are less aggressive than tumors that develop elsewhere in the GI tract.
Generally, the smaller the tumor is when it’s removed, the slower it grows and the less chance it will recur. For example:
- Tumors 2 cm to 5 cm are generally considered low risk
- Slower-growing tumors 5 cm to 10 cm are intermediate risk
- Faster-growing tumors of 5 cm to 10 or more cm are considered high risk
If the tumor was not completely removed, or if the tumor ruptured during removal, there is a greater chance of it recurring.
What kind of monitoring do I need after treatment?
After surgery, the recommended follow-up is examinations every 3-6 months, with CT scans. PET scans are not substitutes for CT scans. Recurrent GIST will usually occur within two years after surgery.
If you take imatinib, or sunitinib, side effects of the drugs need monitoring.
Will insurance pay for Gleevec?
Imatinib (Gleevec) is a genetically engineered, biologic drug classified as targeted therapy. These drugs require a complex development process, and the drugs can be expensive. Some insurance companies or policies may not cover drug costs.
Even when the drug is covered by insurance, co-payments can quickly add up. Check your insurance policy to see if these drugs are covered and find out the copayment amount.
Many drug companies offer financial help for biologic drugs, and pharmacies may offer discount programs. Talk to your doctor or pharmacist to learn more about getting help with your drug costs.