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Frequently Asked Questions in GIST
Questions about GIST
Questions about Glivec® in GIST
- How does Glivec work in GIST?
- What are the side-effects?
- How does Glivec interact with other drugs?
- What if I’m pregnant?
- How do I take Glivec? What’s the dosage for GIST?
- What if I take more Glivec than I should?
- What are my responsibilities?
- What if I have additional questions?
Questions about GIST
GIST is a rare cancer of the gastrointestinal (GI) tract. Most GISTs develop in the stomach or in the small intestine, and a small percentage develops elsewhere along the GI tract. GIST is difficult to diagnose and to treat because it often does not cause any physical symptoms until already advanced.
When GISTs first develop, the tumours stay in one area, such as the stomach. GISTs that stay in their original location are called localised tumours. However, when GISTs advance, they can spread to other parts of the body. When a GIST spreads, it becomes a metastatic tumour. GISTs often grow quite large before they are discovered, and many often spread to other organs, mainly the liver.
A protein called KIT—when abnormal—is thought to be one of the major causes of GIST. Normal cells have a limited life span. The KIT protein, which is located on the surface of normal cells, sends a signal inside the cells that tells them to grow and multiply only as needed. When KIT becomes abnormal, its signal stays on constantly and cells become cancerous and continue to grow and multiply. Cancerous GIST cells have a survival "advantage" because they grow and multiply faster and live longer than the normal surrounding cells. The longer the cancerous cells live, the more potential they have to become dangerous, and the more likely they are to spread to other parts of the body.
Until now, patients with GIST have had very few treatment options.
Surgery has been the main treatment for GIST. However, many GISTs — those that have already spread to another part of the body—cannot be surgically removed. Often, even with surgery, parts of the original GIST remain or GIST returns to another site in the body. In these cases, when surgery really only relieves disease symptoms, it is considered palliative.
Traditional cancer therapies such as chemotherapy and radiation therapy, or radiotherapy, have been ineffective in the treatment of the disease. Because of the lack of effective therapies, and because many GISTs cannot be removed surgically, developing an effective drug therapy was very important. Glivec is the first effective drug approved for treatment of GIST, providing an effective treatment option for GIST patients who previously had no other way to manage their GIST disease.
Questions about Glivec in GIST
Glivec is the only therapy that specifically targets the main cause of GIST. The KIT protein on GIST cells sends out a constant signal that tells the cancerous cells to keep growing and multiplying. Glivec works by blocking, or turning off, the signal from the KIT protein, so the cancerous cells stop growing.
In clinical studies, most patients experienced mild or moderate side effects with Glivec therapy. Most patients are not bothered enough by side effects to discontinue Glivec therapy. The most common side effects include nausea, vomiting, diarrhoea, abdominal pain, fatigue, myalgia, muscle cramps, skin rash, and fluid retention.
Some patients experienced bleeding from the GI tract or the tumour while on Glivec therapy (GI bleeds are more common in GIST than CML). While bleeding may have been caused by the tumour—not Glivec—you should notify your physician immediately if you observe any blood in your stools, have pain in your abdomen, feel weak or dizzy, or look pale.
If you experience any of these symptoms during Glivec therapy, contact your physician, particularly if they are severe
- nausea
- vomiting
- diarrhoea
- abdominal pain
- fatigue
- myalgia
- muscle cramps
- skin rash
- fluid retention
How does Glivec interact with other drugs?
Like many medications, Glivec can affect, or be affected by, other products you may be taking. When this happens, Glivec or the other drugs may lose their effectiveness or produce more severe side-effects. Some drugs that can cause interactions are commonly used over-the-counter medications, such as paracetamol (acetaminophen) or herbal products such as St. John’s Wort. Also, birth control pills (oral contraceptives), blood thinners (especially warfarin), and anticonvulsants might interact with Glivec. In addition, Glivec should not be taken with grapefruit juice. Therefore, it is very important to talk to your physician about all medications and supplements you are currently taking or are planning to take in the future.
If Glivec is used during pregnancy, or if the patient becomes pregnant while receiving Glivec, the patient should be apprised of the potential hazard to the foetus. Women of childbearing potential are encouraged to use effective contraception during treatment. Please discuss these issues with your physician or nurse before beginning therapy with Glivec.
How do I take Glivec? What’s the dosage for GIST?
Glivec is easy to take. Unlike many drugs that must be administered in the hospital, Glivec is available in tablet form and is usually taken by mouth once a day. You should take Glivec with a meal and a large glass of water to minimise GI upset
The standard recommended starting dose for most patients is 400 mg/d1. Glivec is supplied as 100-mg and 400-mg tablets. Your physician will specify which dose you should take and how many of each tablet
Depending on your response to treatment, your physician may decide to change the dose of Glivec that you are taking. If your daily dose is changed, be sure to follow your physician’s recommendations.
What if I take more Glivec than I should?
If you think you may have taken more Glivec than you should have, talk to your doctor immediately. You may require medical attention.
If vomiting occurs, do not take another dose. Contact your physician.
Because Glivec is an oral therapy, you have the important responsibility of ensuring that you take the correct dose every day.
If you experience side-effects, you should talk with your physician.
It is very important for you to continue taking Glivec unless your physician has told you to stop. Contact your physician before stopping your therapy. Following your prescribed dosage is crucial in achieving optimal results. If you are feeling discouraged, talk to your physician, your nurse, or a friend or family member about the way you feel. Getting emotional support during your treatment is just as important as getting medical support.
What if I have additional questions?
If you have additional questions or would like more information, please contact your physician.
You may also choose to access patient support groups, which will allow you to share your experiences with others. Ask your physician for advice on getting additional information.
Find out about efficacy, dosage, and safety in Prescribing Glivec.