Risk stratification is done on the basis of prognostic factors, which include: mitotic rate, tumor size, tumor site, surgical margins (including whether tumor rupture occurred) (5). Contrast-enhanced abdominal and pelvic CT-scan is the preferred imaging for staging and beta-catenin mutation follow-up. Recent studies have demonstrated that

Response Evaluation Criteria In Solid Tumors (RECIST) is an insensitive tool in evaluating GIST treated with imatinib. Another Inhibitors,research,lifescience,medical means of assessment, the Choi criteria, describes a 10% decrease in unidimensional tumor size or a 15% decrease in tumor density on contrast-enhanced CT as an early indicator of response (6). This appears to be more sensitive and more precise than RECIST in assessing the response of GIST to imatinib after 3 months of therapy. This was seen in our case as the patient’s tumor size remained Inhibitors,research,lifescience,medical stable after 3 months of imatinib but there was a decrease in tumor density with multiple foci of air seen in the follow up CT scan. So, CT assessment is a sensitive and specific method to assess the response of GIST to imatinib if evaluated by Choi criteria. Evaluation of FDG uptake using PET scan is useful mainly Inhibitors,research,lifescience,medical when early detection of tumor response to imatinib treatment is of special concern. The standard treatment of localized GIST is complete surgical excision, without dissection

of clinically negative lymph nodes (5). If complete resection is not feasible, or if cytoreduction is desired to allow less aggressive surgery, initial imatinib pretreatment is recommended

(5). Following maximal tumor response, surgery is performed. Inhibitors,research,lifescience,medical Mutational analysis may help to exclude less sensitive mutational status (e.g., PDGFRA D842V mutations) from therapy Inhibitors,research,lifescience,medical with imatinib. PET scan is particularly useful to assess tumor response very rapidly, so that surgery is not delayed in the case of non-responding disease. In patients with locally advanced or metastatic disease, imatinib is the preferred treatment with the standard dose being 400 mg daily (5). Patients with exon 9 KIT mutations fare better in terms of progression free survival on higher doses, i.e. 800 mg daily, which is therefore standard treatment in this subgroup. Treatment should be continued indefinitely since treatment others interruption is generally followed by rapid tumor progression. Close monitoring of tumor response should be continued throughout treatment, since the risk of secondary progression persists over time. The standard approach in the case of tumor progression is to increase the imatinib dose to 800 mg daily. In case of progression or intolerance on imatinib, the second-line standard treatment is sunitinib. This drug was proved effective in improving progression free survival following a ‘4 weeks on -2 weeks off’ regimen. After failing on sunitinib, patients with metastatic GIST should be considered for participation in a clinical trial (5).