Preoperative and Postoperative Imatinib Mesylate Study in Patients With c-Kit Positive GIST

Imatinib mesylate is a drug that may help to kill gastrointestinal stromal tumor cells. Around 3 weeks before your scheduled surgery, you will have a PET scan, a CT scan and two to three tablespoons of blood will be collected. These are imaging tests and are being done to check on the status of the disease. These tests will be repeated the day before your scheduled surgery. If your doctor feels it is necessary, you will have a chest x-ray and 2 to 3 tablespoons of blood will be collected for routine tests. Women who are able to have children must have a negative blood pregnancy test. Before treatment, you will also have a biopsy procedure of the tumor performed. This biopsy is being done to study the effect of imatinib mesylate on the tumor cells. The tissue that is collected during the biopsy procedure will be compared to the tumor that is taken out at the time of surgery. You will be randomly assigned (as in the toss of a coin) to one of three groups. One group will begin taking imatinib mesylate two times a day by mouth starting 7 days before surgery. The second group will start taking imatinib mesylate 5 days before surgery. Participants in the third group will begin taking imatinib mesylate 3 days before surgery. After your surgery, the removed tumor will be studied and compared to the tissue collected before surgery to see what effect (if any) imatinib mesylate had on the tumor. All patients will then continue imatinib mesylate for 2 years after surgery. You will take imatinib mesylate two times a day for 2 years. If you develop any side effects to the study drug, treatment may be temporarily stopped or the dose of the drug changed until the symptoms are gone. If the disease gets worse or you experience any intolerable side effects, you will be taken off the study and your doctor will discuss other treatment options with you. You will be seen by a physician regularly after surgery. Two to three tablespoons of blood will be collected once a month for routine tests, and a you will have a CT scan done every 3 months. These tests will help us determine if your cancer has come back. THIS IS AN INVESTIGATIONAL STUDY. Imatinib mesylate is FDA approved and is commercially available. Up to 48 participants will take part in this study. All will be enrolled at M. D. Anderson.