What You Need to Know About GIST
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.
Prior to this year, imatinib (Gleevec) was used as an adjuvant therapy for high-risk, resected GIST. The therapy was given for one year. Overall survival was improved with this therapy.
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.