In selected higher risk adjuvant situations, imatinib is recommended for 3 years.Imatinib was approved for metastatic and unresectable GIST by the US FDA, February 1, 2002. The two-year survival of patients with advanced disease has risen to 75–80% following imatinib treatment.If resistance to imatinib is encountered, the multiple tyrosine kinase inhibitor sunitinib (marketed as Sutent) can be considered. : 26 and 31 The effectiveness of imatinib and sunitinib depend on the genotype. c-KIT- and PDGFRA-mutation negative GIST tumors are usually resistant to treatment with imatinib, as is neurofibromatosis-1-associated wild-type GIST. A specific subtype of PDGFRA mutation, D842V, is also insensitive to imatinib. Recently, in PDGFRA-mutated GIST, avapritinib has been approved by FDA. Now there are real-world data coming for avapritinib as well (Dr Sameer Rastogi, et al. )Regorafenib (Stivarga) was FDA-approved in 2013 for advanced GISTs that cannot be surgically removed and that no longer respond to imatinib (Gleevec) and sunitinib (Sutent). Epidemiology
GISTs occur in 10-20 per one million people. The true incidence might be higher, as novel laboratory methods are much more sensitive in diagnosing GISTs. The estimated incidence of GIST in the United States is approximately 5000 cases annually. : 1063  This makes GIST the most common form of sarcoma, which constitutes more than 70 types of cancer. The majority of GISTs present at ages 50–70 years. Across most of the age spectrum, the incidence of GIST is similar in men and women. : 1122 Adult GISTs are rare before age 40. Pediatric GISTs are considered to be biologically distinct.
In a CT scan, abnormalities may be seen in 87% of patients and it should be made with both oral and intravenous contrast. Among imaging studies, MRI has the best tissue contrast, which aids in the identification of masses within the GI tract (intramural masses). Intravenous contrast material is needed to evaluate lesion vascularity. Preferred imaging modalities in the evaluation of GISTs are CT and MRI,: 20–21  and, in selected situations, endoscopic ultrasound. CT advantages include its ability to demonstrate evidence of nearby organ invasion, ascites, and metastases. The ability of an MRI to produce images in multiple planes is helpful in determining the bowel as the organ of origin (which is difficult when the tumor is very large), facilitating diagnosis. Small GISTs
Since GISTs arise from the bowel layer called muscularis propria (which is deeper to the mucosa and submucosa from a luminal perspective), small GIST imaging usually suggest a submucosal process or a mass within the bowel wall. In barium swallow studies, these GISTs most commonly present with smooth borders forming right or obtuse angles with the nearby bowel wall, as seen with any other intramural mass. The mucosal surface is usually intact except for areas of ulceration, which are generally present in 50% of GISTs. Ulcerations fill with barium causing a bulls eye or target lesion appearance. In contrast-enhanced CT, small GISTs are seen as smooth, sharply defined intramural masses with homogeneous attenuation.