As with other gastrointestinal cancers, treatment for gastrointestinal stromal tumors (GIST) usually starts with surgery. These relatively rare tumors are caused by specific proteins in cells that help move food through the digestive system. After surgery, GIST responds best to drugs aimed at stopping those overactive proteins, rather than to traditional forms of chemotherapy and radiation.
Finding the Tumors
To treat GIST, a doctor must first find the tumors. Suspicious areas can be found using tests like X-rays, CT scans, and MRI scans. Patients may drink a barium "milkshake" or take a barium enema to enhance X-ray images. An endoscope, a tiny flexible tube with a video camera, may be inserted into the GI tract for a closer look.
Determining if a Tumor Is Malignant
Radiology tests can find tumors but can't tell if they're cancer. Doctors may remove a few cells to find out. But GISTs are hard to biopsy because they grow beneath the lining of the stomach or intestines. Surgeons may try to take a tiny sample by looking down the esophagus and into the stomach with a long tube called an endoscope. Or they may insert a long needle through the skin to get a biopsy. Often it's best to remove the tumor and then test it.
Testing Samples for GIST
To find out if a tumor is a GIST, it's important to test for the genes that contain key proteins, especially a gene called c-KIT. Pathologists use antibody tests that change color if tumor has the c-KIT gene. They also look at tissue to see how fast cells are multiplying. This is called the mitotic rate.
Deciding on GIST Treatment
Doctors assign a stage -- ranging from I to IV -- to GIST using four factors:
- Size of the primary tumor
- Whether lymph nodes are involved
- If it spread, or metastasized, to other organs
- How fast cells are multiplying
The higher the stage, the more serious the disease. Treatment depends on the stage of the cancer.
Deciding Whether to Operate
Surgery is the best way to treat GIST, so it's always the first choice, even if it means removing parts of surrounding tissue or organs. However, some tumors may have spread into vital tissue or into other parts of the body, making them impossible to cut out. In those cases, medication can be used to shrink tumors so they're small enough to operate on.
The scope of surgery often depends on the severity of the disease. Small tumors may be removed using a laparoscope, a fiber optic instrument that can be inserted through a small cut. Larger tumors may require removal of parts of affected organs, like the intestine or liver. GIST rarely spreads into nearby lymph nodes, so those usually don't have to be removed.
Problems Before and After Surgery
Before surgery, large tumors may block, tangle, or tear intestines. They may also cause internal bleeding that requires IV fluids or even transfusions. Post-surgery problems are similar to any major GI surgery, including infections, bowel obstruction, and heart and lung problems. Follow-up care is critical. If part of the stomach has been removed, the patient will have to make some diet changes.
Drug Therapy for GIST
The risk of GIST coming back depends on the size of the tumor and how fast it was growing. Follow-up medication is important. A recent study showed that three years of medical treatment significantly improves long-term survival rate. Even if GIST isn't operable, medication may improve survival or reduce problems caused by large tumors. Medication may also shrink a large tumor to make it surgically removable.
Medication for GIST
Medication can often be used to treat GIST. Imatinib (Gleevec) can be highly effective, especially for advanced-stage GIST. It blocks the mutating proteins that cause tumors to grow. Studies show that imatinib helps control GIST in 9 out of 10 people following surgery, and long-term treatment with imatinib can control GIST for at least three years. Imatinib can help before surgery to shrink tumors and after surgery to lower the risk of the cancer coming back. It's also used for inoperable tumors.
Another Medication Alternative
When imatinib doesn't work, sunitinib (Sutent) is another option. It can also slow down the disease and shrink tumors. Sunitinib is also a possibility when a patient has side effects from imatinib and the doctor wants to try another drug treatment.
Experimental Therapies for GIST
With advances in genetic research, other medications, such as dasatinib (Sprycel), nilotinib (Tasigna), or sorafenib (Nexavar), are being studied as treatment options for GIST. Some of them work the same way as imatinib and sunitinib. Others attack overactive proteins in completely different ways. Some patients are candidates for experimental trials. Ask your doctor about clinical trials that might be a possibility for you.