Cancer is probably the one word no one wants to hear. If you’ve recently been diagnosed with a gastrointestinal stromal tumor (GIST), a relatively rare cancer found in the digestive tract, you might be frightened, overwhelmed, and concerned about what happens next.
WebMD talked to experts who shared some facts you should know if you’ve been diagnosed with GIST. “It's important for people diagnosed with GIST to understand that this is a different type of cancer that can range from very slow-growing -- in the vast majority of cases -- to aggressive in a minority of cases,” says Nikhila Khushalani, MD, Section Chief for Soft Tissue and Melanoma at the Roswell Park Cancer Institute in Buffalo, N.Y.
What is GIST?
Most cancers are called “carcinomas,” and they develop in the skin or in the lining of internal body structures like the stomach. But GIST is a bit different: it is one of a group of cancers that are called sarcomas. These cancers develop in the connective or supportive tissues of the body like fat, muscle, or bone.
Until the late 1990s, doctors didn’t really understand that GIST was different from other kinds of cancers found in the stomach and digestive system. That’s when they learned that the cells of tumors make a specific protein called KIT, and that 95% of GIST tumors have mutations or changes in the gene that makes the KIT protein.
How is GIST Diagnosed?
GIST is a more difficult kind of cancer to diagnose than more common cancers like breast and prostate cancer. While a doctor may suspect that a particular cancer is GIST based on how it looks on a CT scan, the only way to be sure is through pathology -- studying the tumor cells in a laboratory.
Because it is a complex diagnosis, it’s very important that GIST be diagnosed and treated by a multidisciplinary team that has experience with this type of tumor.
How is GIST Treated?
GIST has become a treatable cancer. Surgery is the primary treatment of GIST if the disease has not spread and is resectable. In fact, in many cases once the original tumor is surgically removed, you may not need further treatment at all.
“Many people are cured by some fairly simple surgery,” says George Demetri, MD, associate professor of medicine at Harvard Medical School and director of the Center for Sarcoma and Bone Oncology at the Dana-Farber Cancer Institute and Brigham and Women's Hospital in Boston. “Well over half of all cases of GIST are small, low-grade tumors and easily removed surgically.”
Once the tumor is removed surgically, the tumor will be examined under a microscope to try to confirm the diagnosis and to test the tumor for certain mutations.
There are certain factors that make GIST more likely to recur:
- Tumor size. The larger the tumor, the more likely it is to recur after surgery. Small-sized GISTs may recur as well. Therefore, size is only one variable for recurrence.
- The “mitotic index.” This means the proportion of cells that are making copies of themselves. The higher the mitotic index, the higher the risk of recurrence.
- Tumor location. GIST that is found in the stomach is less likely to recur as compared to GIST found in other sites of origin.
Based on these factors, the risk of recurrence of GIST is classified as low, intermediate, or high.
“For probably seven out of 10 patients whose tumors can be surgically removed, the pathology report will tell us that they don’t have a big risk of the cancer ever coming back -- maybe 10% in their entire lifetime,” says Demetri.
Regardless of recurrence risk, everyone with a diagnosis of GIST should be evaluated at 3- to 6-month intervals.
CT scans of the abdomen and pelvis should also be performed every 3 to 6 months. PET scans are not a replacement for CT scans.
A subsequent study was performed using Gleevec for either three years or one year. The three-year duration was superior to the one-year duration. The three-year duration for adjuvant imatinib has been approved by the FDA, for routine use after surgery for intermediate to high-risk GIST.
“It’s clearly been shown that Gleevec can reduce the risk of GIST recurrence, and in high-risk patients, it even improves their overall survival rates,” says Khushalani.
For individuals with the PDGFRA mutation, Gleevec is not recommended. The presence of this gene mutation results in imatinib resistance, but also results in a reduced risk of recurrent GIST.
What if the Cancer Has Spread?
In 15% of cases, GIST cannot be completely removed with surgery. In this case, Gleevec has been used prior to surgery, to attempt to shrink the tumor and make surgery possible. This therapy, known as neo-adjuvant therapy, was found to be safe and effective and therefore should be used on a case-by-case basis. However, if the tumor still remains unable to be surgically removed, imatinib should be continued after surgery.
“Depending on the size of the tumor or where it is located, we might not be able to get it all -- at least not without doing real damage to the person’s ability to function,” says Demetri. For example, taking out a large tumor at the end of the stomach, where it empties into the duodenum, could so damage your digestive system that you might never be able to eat or eliminate waste normally.
For a few people who are diagnosed with GIST, the disease has already metastasized, meaning that it has spread beyond the area where it started in the digestive system and into other places in the body.
Metastatic GIST is disease that has spread outside of the site of origin of the primary tumor. This disease cannot be removed surgically. In these cases, the use of imatinib is the treatment of choice. Response rates and disease stability are approximate 90%. Long-term survival (9 years) is 35%.
“Between 10% and 20% of GIST patients have disease that’s spread right from the start,” says Demetri. “That’s frightening, but the good news is that Gleevec is very effective in controlling metastatic GIST. It works in about nine out of 10 patients and keeps the disease under control for an average of about 2 years. But about 17% of our patients with metastatic disease who were in the initial trial that we did of Gleevec to treat GIST are still alive and taking the drug today, 12 years later,” he says.
For people whose GIST progresses, or who cannot take imatinib, the drug sunitinib (Sutent) may provide benefit. With this drug, the response rates and disease stability is over 50%, with a survival rate of over two years.
The drug regorafenib (Stivarga) is used to treat patients who have tumors that cannot be surgically removed and no longer respond to other GIST treatments.
Back in the mid-1990s, doctors didn’t have much to offer people with GIST, but that has changed. “Today we have excellent treatment options, with new therapies being studied in clinical trials,” says Demetri. “We’ve made enormous progress over the past 10 years in treating GIST, so there’s a lot of hope for patients.”
For more information and to connect with other people who have GIST, visit GIST Support International: www.gistsupport.org.