Doctors use many tests to find, or diagnose cancer. In addition to a physical examination, the following tests may be used to diagnose a GIST and then determine the stage or extent of spread of the cancer in order to determine the best treatment. Not all tests listed will be used for every person.1,2
Barium swallow: The patient swallows a liquid containing barium and then a series of x-rays are taken. Barium coats the surface of the esophagus and upper GI tract, making cancer or other unusual changes easier to see on the x-ray. If there is an abnormal looking area, an upper endoscopy and biopsy to find out if it is cancerous is typically performed. A barium enema may also be used to evaluate the lining of the colon and rectum on an x-ray after the barium has been given through the anus.
Endoscopy: Endoscopy allows the doctor to see the inside of the esophagus, stomach or intestines. During an “upper” endoscopy, the doctor inserts a thin, lighted tube called an endoscope through the mouth, down the esophagus, and into the stomach and small bowel. With “lower” endoscopy, the scope is inserted through the anus. If abnormal areas are found, the doctor can remove a sample of tissue and check it for evidence of cancer by performing a biopsy.
Computed Tomography (CT) Scan: A CT scan is a technique for imaging body tissues and organs, during which X-ray transmissions are converted to detailed images, using a computer to synthesize X-ray data. A CT scan is conducted with a large machine positioned outside the body that can rotate to capture detailed images of the organs and tissues inside the body.
Magnetic Resonance Imaging (MRI): MRI uses a magnetic field rather than X-rays, and can often distinguish more accurately between healthy and diseased tissue than a CT. An MRI gives a better picture of cancer located near bone than does CT, does not use radiation, and provides pictures from various angles that enable doctors to construct a three-dimensional image of the cancer.
Positron emission tomography (PET): Positron emission tomography scanning is an advanced technique for imaging body tissues and organs. One characteristic of living tissue is the metabolism of sugar. Prior to a PET scan, a substance containing a type of sugar attached to a radioactive isotope (a molecule that emits radiation) is injected into the patient’s vein. The cancer cells “take up” the sugar and attached isotope, which emits positively charged, low energy radiation (positrons) that create the production of gamma rays that can be detected by the PET machine to produce a picture. If no gamma rays are detected in the scanned area, it is unlikely that the mass in question contains living cancer cells. PET may be helpful in detecting resistance to treatment and for the very early assessment of response to therapy.
Endoscopic ultrasound: This test is similar to an endoscopy, but the scope has a small ultrasound probe on the end. The probe uses sound waves to create an image of the stomach or rectum and nearby organs. The ultrasound image helps doctors determine if or how far the cancer has spread into nearby tissues.
Biopsy: Your doctor may recommend a biopsy if a mass suspected of being a GIST or other cancer is found. A biopsy is the removal of a small amount of tissue for examination under a microscope. The type of biopsy performed will depend on the location of the suspected cancer. Other tests can suggest that cancer is present, but only a biopsy can determine a definite diagnosis.
Genomic or Biomarker Testing-Precision Cancer Medicine
The purpose of precision cancer medicine is to define the genomic alterations in the cancers DNA that are driving that specific cancer. Precision cancer medicine utilizes molecular diagnostic & genomic testing, including DNA sequencing, to identify cancer-driving abnormalities in a cancer’s genome. Once a genetic abnormality is identified, a specific targeted therapy can be designed to attack a specific mutation or other cancer-related change in the DNA programming of the cancer cells. Precision cancer medicine uses targeted drugs and immunotherapies engineered to directly attack the cancer cells with specific abnormalities, leaving normal cells largely unharmed. Treatment for a GIST can start before this testing is completed. Test results however may change the treatment plan.
Testing of GIST helps determine which precision cancer medicine is best to target the specific mutation causing the tumor to grow. Studies have also shown that depending on the tumor’s specific gene mutations, some patients may need higher doses of a drug called Gleevec (imatinib) to best control the tumor. Otherwise, they might not benefit from taking this drug at all.
A GIST may have one of several different mutations, some of which are more harmful than others. Different mutations have different prognoses and treatment. Approximately 85% of GIST contain oncogenic mutations in one of two receptor tyrosine kinases: KIT or PDGFRA (platelet-derived growth factor receptor alpha).3 Activation of either of these receptor tyrosine kinases plays a central role in the pathogenesis of GIST.4,5
When a GIST has a mutation that is not recognized by current tests, it is referred to as “wild type” (WT). Wild-type tumors, with no detectable KIT or PDGFRA mutations, account for 12% to 15% of all GIST.3
Learn more here: http://oncoprecision.org/
1 Casali PG, Jost L, Reichardt P, et al.: Gastrointestinal stromal tumors: ESMO clinical recommendations for diagnosis, treatment and follow-up. Ann Oncol 19 (Suppl 2): ii35-8, 2008.
2 Demetri GD, Benjamin RS, Blanke CD, et al.: NCCN Task Force report: management of patients with gastrointestinal stromal tumor (GIST)–update of the NCCN clinical practice guidelines. J Natl Compr Canc Netw 5 (Suppl 2): S1-29; quiz S30, 2007.
3 Miettinen M, Lasota J: Gastrointestinal stromal tumors: review on morphology, molecular pathology, prognosis, and differential diagnosis. Arch Pathol Lab Med 130 (10): 1466-78, 2006.
4 Hirota S, Isozaki K, Moriyama Y, et al.: Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors. Science 279 (5350): 577-80, 1998.
5 Heinrich MC, Corless CL, Duensing A, et al.: PDGFRA activating mutations in gastrointestinal stromal tumors. Science 299 (5607): 708-10, 2003.