Understanding GIST:Know what to expect

Understanding your disease

How common is GIST?

You, your care partners, and your care team may have all been surprised by a GIST (gastrointestinal stromal tumor) diagnosis. After all, it is a fairly rare condition with only 4,000-6,000 cases identified each year in the US. Only about 1% of gastrointestinal cancers are GIST. GIST can happen at any age, but is more common in people older than 50.

GIST: The basics

It's not clear exactly what causes GIST. GIST may be found in the esophagus, stomach, colon, small intestine, or rectum. No lifestyle or environmental factors have been identified, though most people with GIST do have a gene mutation, which may drive tumor development. Why that mutation happens to some people has not been determined. If the GIST tumor can be removed with surgery, it's known as "resectable GIST." Advanced GIST is defined as GIST that can no longer be treated with surgery alone, or has come back, or has spread to another part of the body. If GIST cannot be treated with surgery, there are other treatment options available. There are a number of tyrosine kinase inhibitors, or TKIs, a targeted medication, approved to treat GIST.

GIST may be something that you're living with for a very long time. It's important to remember that the GIST you're living with today may be different from the GIST you have later. Your treatment needs and personal needs may change, too. Because your treatment needs may change, and due to the rarity of the disease, it's important to find a GIST specialist.

What is disease progression?

Disease progression means that cancer cells may be growing, the tumor may be getting bigger, or it may be spreading.

What causes it?

Disease progression can happen if genes continue to change (mutate), which means that someone with GIST can have new and different mutations over time. If that happens, a treatment could stop working, even if it worked before. This is called drug resistance. You should always speak to your doctor about your GIST treatment. You may not be aware that your GIST treatment is no longer working, or you may develop new symptoms that signal something is wrong. Because it may be hard to tell on your own, it's important to have follow-up appointments and tests with your care team.

Not sure what to ask at your next GIST doctor's appointment?

Keeping up with tests is very important

Whether you’ve had surgery or not, committing to follow-up testing is very important. Even if all the cancer was removed, it can come back. And even if you are taking medication as your doctor instructs, a GIST may still grow. Someday you may need more surgery or a different treatment. For some people, this may happen quickly. For others, it may take several years.

• When your GIST was first diagnosed, you may have had tests including PET, CT/CAT, MRI, bone scan, endoscopy (upper, lower, capsule), ultrasound, biopsies, and/or blood tests. You may have some of these tests again later on.
• Many doctors also recommend genetic testing (or genotyping) before choosing a treatment. This is helpful because some drugs target certain genes associated with cancer. And some genetic mutations can affect how well certain drugs work. You may be tested for KIT (exon 9, 11, 13, and 17) and/or PDGFRα (exon 12 and 18).
• As the months and years pass, your main follow-up will include imaging (CT, MRI, PET, FUSION PET‑CT) and blood tests. These will help determine if your GIST has grown or spread. They can also show whether your current treatment is still effective or needs to be changed.

For more information about gene mutations, see below.

About GIST mutations

All cancers, including GIST, begin when one or more genes in a cell mutate. A mutation is a change that’s usually caused by damage to genes in a cell at some point during a person’s life. It’s not clear why this happens.

Genes make proteins that control how cells work. Mutated cells can create abnormal proteins or prevent proteins from forming. Either can cause cells to multiply and become cancerous.

Your doctor may recommend that you get genetically tested for your mutation as part of your GIST treatment. Knowing your gene mutation type can help your doctor give you the best possible treatment and avoid drugs that may not work well. For some patients with low‑risk GIST, your doctor may decide mutational testing is not necessary.

Primary mutations are responsible for starting the growth of GIST. In people with GIST, the most common primary gene mutations are:

• KIT (70-80%)
• PDGFRα (5-10%)
• WILD TYPE (no KIT or PDGFRα mutations, 10-15%)

Sometimes, genes can continue to mutate. Over time, someone with GIST can develop new and different mutations, called secondary mutations.

The most common secondary mutations in people with advanced GIST are:

• KIT (~97%)
• PDGFRα (~3%)

If genes continue to mutate, your GIST may stop responding to a certain treatment or become resistant. When a GIST becomes resistant to a drug, a new treatment should be tried.

Not sure what to ask at your next GIST doctor's appointment?

New GIST treatments are always being developed

Some people with advanced GIST consider joining a clinical trial for the chance to try a new treatment that is not approved by the FDA for GIST yet. But there may be risks with clinical trials. So, you should learn everything you can about them and speak with your care team before joining.

You can read about new trials for GIST treatments at Life Raft Group’s Clinical Trials website. The National Cancer Institute and The National Institute of Health also offer information about clinical trials.

Also, be sure to sign up for ongoing education, support, and information about future treatments from GISTTogether.

Where can you learn more about GIST?

Here are some sites where you can learn more about GIST:

• American Cancer Society
• Cancer.net
• The GIST page from the Dana‑Farber Cancer Institute
• GIST Support International
• The Life Raft Group
• The Mayo Clinic
• National Cancer Institute