Recommendations for diagnostics and therapy of gastrointestinal stromal tumors (GIST) in 2010 Recommendations

Abstract

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of gastrointestinal tract. Advances in the understanding of the molecular mechanisms of GIST pathogenesis have resulted for last years in the emerging of GIST as a distinct sarcoma entity. The paper describes guidelines for diagnostics and therapy of these tumors based on scientific basis and experts’ experience, which are commonly accepted and worth to recommend. Overexpression of KIT receptor, as a consequence of mutation of protooncogene KIT, is highly specific for GIST and enable for detection by immunohistochemistry staining (CD117) in tumor specimens. It is the most important criterion in microscopic diagnostics and indications for treatment with small-molecule tyrosine kinas inhibitors. Sending material for molecular analysis is strongly recommended (for KIT and PDGFRA genotyping). Radical surgery is still the mainstay treatment for primary, localized, resectable GISTs, although high percentages of the patients after potentially curative operations develop recurrent or metastatic disease. In inoperable/metastatic lesions the treatment of choice is tyrosine kinase inhibitor – imatynib mesylate – the first effective systemic therapy in advanced CD117(+) GIST. Recommended initial dose should be 400 mg daily (800 mg for exon 9 KIT mutants). Monitoring of the therapy should be based on serial computed tomography imaging of abdominal cavity with the assessment of changes of tumor size and density. In case of disease progression the increase of imatynib dose to 800 mg daily is recommended and if further progression exists – sunitinib in the initial dose 50 mg daily should be introduced. Clinical trials evaluating the role of surgery in combination of imatynib and the efficacy of other molecular targeted drugs in resistant cases are ongoing. Existing data indicate beneficial role of adjuvant imatynib therapy in terms of relapse-free survival, especially in group of patients with significant risk of relapse.. Presented recommendations for diagnostics and therapy of GIST should be practically implemented by physicians involved in management of GIST patients in Poland. The including GIST cases in national Clinical Registry (http://gist.coi.waw.pl) and standard treatment of patients in multidisciplinary team with expertise in GIST therapy, as well as enrollment of new cases to prospective clinical trials, are recommended.