Recommandations pour la prise en charge des tumeurs stromales gastro-intestinales (GIST)

Background: The management of gastrointestinal stromal tumors (GIST) has evolved very rapidly in the last years. A national consensus meeting was therefore organized in order to identify the optimal management procedures for patients with GIST in localized and advanced stages. Methods: A panel of different specialties, including pathology, molecular biology, imaging, surgery, gastroenterology, medical oncology reviewed the current literature, in particular the recent Lugano conference, to identify consensus points and topics for future research in four different working groups: pathology and molecular biology, early management of small tumors and imaging, surgery, and medical treatment. Consensus points were categorized according to the Standard Options Recommandations (SOR) of the French Federation of Cancer Centers. Results: The standard histological examination with immunohistochemical analysis using CD117, CD34, PS100, desmin and smooth muscle actin is considered standard. Molecular biology for the identification of KIT and PDGFRA mutation is advisable for GIST with negative CD117 staining, and otherwise is considered a research procedure. Complete tumor resection with negative tumor margins is the standard surgical treatment. Adjuvant imatinib after optimal tumor resection as well as neo-adjuvant imatinib remain experimental approaches to be performed within prospective clinical studies. Imatinib should be started at the date of diagnosis of metastatic relapse and given until development of intolerance or progressive disease. Resection of metastases is also considered as an experimental procedure which can not be recommended routinely. The criteria for tumor response to imatinib should include not only tumor size reduction or disease stabilization, but also reduction of tumor density (Hounsfield units) on computed tomography, metabolic activity (i.e. reduction of FDG uptake on positron emission tomography), and reduction of vascularisation of the tumors using contrast enhanced ultrasound evaluation. An increase in tumor size may be associated with pathologic response to imatinib therapy, and available survival data indicate that the survival of these patients is similar to that of patients with conventional tumor response. Conclusions: Consensus points in clinical management of GIST in this national conference adopted the majority of consensus points published in the Lugano conference. This multidisciplinary work will be published in the reference oncology, gastroenterology, and pathology journals in French languages.