Gastrointestinal Stromal Tumor (GIST)
GIST (gastrointestinal stromal tumor) is a relatively rare type of cancer that affects an estimated 5,000 to 10,000 new people each year in the U.S. Most GIST tumors develop in the stomach; but they also can arise in the small intestine, colon and rectum, esophagus or abdominal cavity.
GIST tumors are derived from the pacemaker cells that stimulate movement of the gut. As sarcomas (tumors of connective tissues), GISTs have different characteristics than much more common cancers of the digestive tracts (called "carcinomas"). Therefore, GIST requires a different type of specialized treatment. Treatment of this rare cancer is most effective when directed by cancer specialists who have experience and focused expertise on GIST.
Until about 20 years ago, GISTs were actually thought to be a totally different type of cancer. The discovery of the molecular switch, called KIT, that turns on the growth of GIST has made it possible to diagnose GIST, and has led to the development of specific drugs that target the growth of this cancer.
The GIST team at the University of Chicago Center for Gastrointestinal Oncology is led by physicians with extensive experience in identifying, treating and researching GIST. With its advanced expertise in this rare cancer, the GIST program draws patients from across the U.S.
Early symptoms of GIST may go unnoticed. And, because GIST is so rare, primary care physicians may not readily recognize its symptoms. Without early detection and treatment, the primary tumor can grow very large or spread (metastasize) to other locations in the body, such as the liver or abdominal cavity. A GIST tumor that originates elsewhere and then spreads to the liver is still biologically a "GIST" tumor and not a liver tumor; therefore, GIST tumors in the liver are treated very differently than cancer which starts in the liver ("liver cancer").
Accurate diagnosis is the first step toward treatment. When GIST is suspected or confirmed, it is especially helpful to seek treatment from specialists with experience and expertise in this cancer.
The University of Chicago Center for Gastrointestinal Oncology offers thorough diagnostic procedures aimed at getting the right answers for patients promptly and as comfortably as possible. Diagnostic procedures may include:
- Computed tomography (CT scan). CT scanning is usually the first step of diagnosis. Physicians use the CT scan to identify the precise location of the tumor, and to determine whether it has spread to the liver or other organs.
- 256-channel multi-detector CT (MDCT) scanner. Physicians here can use advanced multi-detector technology, including 256-slice CT imaging, to provide vivid three-dimensional images of GIST tumors very quickly.
- Endoscopic ultrasound (EUS). Performed by gastroenterologists (GI doctors) who specialize in GI endoscopy, this minimally invasive technique uses a high-definition probe to provide very clear images inside the digestive tract. Endoscopic ultrasound can be helpful to clarify the diagnosis for some patients. For example, the physician may use endoscopic ultrasound to obtain a tissue sample (biopsy), which is then analyzed to determine the type of cancer and its staging (how far advanced the cancer is). This information is essential for determining the appropriate course of treatment. EUS also may be used to help the surgeon precisely plan surgical removal of the tumor. Because the GIST tumor is often located in the submucosa (under the surface layer) it can be missed with the routine endoscopic procedures done at other institutions, but it can be readily identified with an EUS.
The CT scanner, multi-detector CT and advanced endoscopic ultrasound technologies provide vivid, detailed images of tumors, which are especially useful for planning surgery to remove the tumor while sparing healthy tissue surrounding the tumor, and for learning whether the cancer has spread (metastasized) to other locations beyond the primary tumor. All of these imaging studies have limitations--CT or EUS may not identify very small tumors or metastatic lesions.
Additionally, tissue biopsy analysis is a key part of the diagnostic process for many patients. Cytopathologists (physicians who specialize in cellular analysis of tissue) work side-by-side with other University of Chicago physicians throughout diagnostic procedures. The cytopathologist analyzes tissue samples at a cellular level to determine whether a tumor is a GIST (sarcoma) or a carcinoma. Because the two categories of cancer are very different, understanding this distinction is essential for appropriate treatment. The cytopathologist may perform molecular stains or do other tests to identify key characteristics of the tumor and determine its chromosomal abnormalities.
Sophisticated Pathology Analysis
Thorough lab analysis by University of Chicago pathologists experienced with GIST will identify certain important features or markers of the GIST tumor, such as whether it is "KIT-positive." Determining whether the KIT (CD117) are present in a tumor is essential for guiding appropriate treatment. The University of Chicago Center for Gastrointestinal Oncology has the expertise to finely analyze KIT and mutational characteristics in order to further fine-tune our diagnosis.
State-of-the-art technology and excellent communication between the physicians allows for rapid diagnostic results, so patients can avoid repeat biopsies and can begin appropriate treatment immediately. Having the cytopathologists working in the same room where the endoscopy or other diagnostic procedure occurs means that some patients can avoid undergoing multiple sessions for testing and initial treatment. Diagnosis and surgery can be accomplished all during the same procedure time. Some tests, such as chromosomal analysis, require additional time to complete.
Treatment recommendations are based on a comprehensive analysis of the GIST genetic mutations, location, stage, and whether it has spread (metastasized) to other areas of the body. Each person’s treatment plan is customized to the specifications of their disease and overall health. However, some general treatment guidelines apply. Treatment for GIST may include:
Surgery is the primary curative treatment for localized GIST (early-stage GIST that has not spread beyond the primary tumor site). Experienced University of Chicago surgeons may perform open surgery or minimally invasive laparoscopic surgery to remove the tumor. Treatment is highly individualized, so the choice of which type of surgery to use is based on factors such as the patient’s unique health characteristics, the size of the tumor and its location. Removal of lymph nodes is not necessary when removing a GIST tumor.
Whether using minimally invasive or more traditional "open" surgery techniques, it is important to remove the tumor and its surrounding pseudocapsule without rupturing it. (The pseudocapsule is tissue that completely surrounds the tumor, like a balloon wrapped around the tumor).
Medical treatment usually involves either imatinib mesylate (Gleevec®) sunitinib (Sutent®), or investigational drugs through clinical trials. The use of imatinib has dramatically improved treatment results for adults with c-KIT (CD117 positive) GIST. This drug may be used before surgery (to shrink a tumor), and it may be recommended in selected patients after surgery to help keep the cancer from coming back. Patients who are unable to undergo surgery will generally receive treatment with imatinib until their tumor becomes resistant to that drug, then other agents are offered.
Imatinib is a targeted therapy that is directed to the exact molecular abnormality, c-KIT, that drives the GIST tumor. Thus it is different from traditional types of chemotherapy, which destroy both cancerous and non-cancerous cells and cause unpleasant side effects. Its selective targeting of proteins means that imatinib can be highly effective and minimizes side effects. Taken daily as a pill, imatinib has been shown to control metastatic, KIT-positive GIST for an extended period in many patients, with minimal side effects.
However, after months or years of imatinib the cancer may develop a resistance so the drug loses its effectiveness. When treatment begins to fail, University of Chicago medical oncologists with expertise in GIST can offer treatment with multiple novel agents, including sunitinib or investigational drugs available only through clinical trials.
Radiation therapy is not an effective option for treating GIST. There is no data that indicates that external beam radiation therapy decreases recurrence or improves overall survival in patients with GIST.
Clinical Trials and Other Research
As a leading center with specialists focused on GIST, the University of Chicago Medicine Comprehensive Cancer Center is involved in clinical trials of many promising anti-cancer drug therapies. Patients with GIST have access to multiple studies of new therapies. We are actively involved in developing trials of novel agents and in recruitment of patients for these trials.
In addition to testing the safety and effectiveness of the newest drug therapies targeting GIST, physicians here are actively involved in research to fine-tune usage of standard drugs in treating GIST. Studies here are probing questions such as whether and for how long imatinib should be taken after surgical removal of GIST tumors.
Integrated Team of GIST-Focused Specialists
Patients at the University of Chicago Center for Gastrointestinal Oncology benefit from an integrated team of specialists -- each of whom has vast experience and advanced expertise in addressing GIST. Our team includes medical oncologists, surgical oncologists, pathologists, nurses with advanced training, and other healthcare professionals. These specialists meet formally as a "tumor board" every week and informally on a near-daily basis. They truly work as a multidisciplinary team to address each patient’s needs every step of the way.
Easing the Patient Experience
We understand that the maze of tests, doctor appointments and consultations can be overwhelming, especially when you’re faced with cancer. That’s why we’ve set up a single point of contact within the Center for Gastrointestinal Oncology -- to ease each patient’s experience at the University of Chicago Medicine. Scheduling all of your diagnostic procedures and doctor visits here will be well coordinated. Often, patients can obtain all necessary tests and meet with both the surgeon and medical oncologist on a single day.