Traitement des tumeurs stromales digestives

[Gastrointestinal Stromal Tumors "GIST": status and news through our experience on 54 cases and review of literature]

Les Tumeurs Stromales Gastro-intestinales « GIST » sont une forme très rare de cancers du tube digestif appartenant à la famille des sarcomes. Le but de ce travail est d'établir le profil épidémiologique et évolutif ainsi que les difficultés diagnostique et thérapeutique de cette pathologie maligne prise en charge dans un pays en développement. Une Etude rétrospective étalée sur 8 ans de Janvier 2002 à Mars 2010, a été mené au Service de Radiothérapie et d'Oncologie du CHU de Casablanca (Maroc) ayant colligée 54 cas de tumeurs stromales gastro-intestinales. L'âge moyen de nos patients était de 55 ans. Le délai moyen d'évolution était de 11 mois (0-72 mois). La biopsie a permis de confirmer le diagnostic dans 14 cas et la chirurgie dans 40 cas. La principale forme histologique était fusiforme (92,6%). Les GIST dans notre série avaient une taille tumorale moyenne de 12,5 cm avec un C-Kit positif dans 52 cas. Le risque évolutif a pu être établi dans 47 cas dont 39 avaient un risque élevé. La chirurgie était le principal traitement des patients de notre sérieAprès un recul moyen de 31 mois, la moitié des patients évaluables de notre série (n=19) est en rémission complète maintenue, le tiers (n=13) est décédé alors que le quart (n=8) présente une récidive locale et /ou métastatique. Quoique les recommandations soient éditées pour la prise en charge de ces tumeurs, ces dernières soulèvent encore de nombreux problèmes aussi bien diagnostiques que thérapeutiques dans notre contexte.

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B. Landi Gastrointestinal stromal tumors (GISTs) are the most frequent intramural mesenchymal tumors of the GI tract, mainly developed in the stomach (65% of cases). Endoscopy is the main diagnostic tool for tumors of moderate diameter (<5cm). Endoscopic ultrasonography (EUS) is the best procedure to differenciate GISTs from other submucosal tumors. Fine-needle aspiration biopsies (FNABs) allow to obtain an histological diagnosis if necessary. Surgery remain the gold standard of treatment for localized GISTs, whereas endoscopic resection is not recommended for these tumors.

[Gastrointestinal stromal tumors: role of computed tomography before and after treatment]

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. They are generally located in the stomach or the small bowel and the potential for becoming malignant varies. Due to their expression of c-kit protein, a positive diagnosis as well as a specific targeted treatment by molecular biology (imatinib) are available. Computed tomography is the best imaging method for diagnosis, staging and follow-up of GIST. They appear as a well-defined exophytic mass with heterogeneous enhancement after intravenous injection of iodinated contrast material. They may contain areas of necrosis and/or haemorrhage and enlarged lymph nodes are exceedingly rare. Most common metastatic sites are the liver and mesentery. Large tumour size and liver or mesenteric metastases are computed tomography criteria for a high malignant potential. After treatment, decrease in tumour size, number and density of lesions and the disappearance of enhancing nodules suggest a positive response to imatinib therapy, whereas a new enhancing nodule within a mass is the usual pattern of recurrence. Positron emission tomography may be useful in specific cases when clinical data are inconsistent with computed tomography criteria.

[The role of PET scan in gastrointestinal stromal tumors]

Abdominal CT is considered the imaging method of choice for the staging and treatment monitoring of Gastrointestinal Stromal Tumors (GIST). The role of Whole-body FDG-PET seems limited for staging because of the low rate of extra-abdominal tumoral involvement and lower sensitivity than CT. However, PET provides assessment of therapeutic response to imatinib as early as 8 days after treatment is begun. The decrease in the metabolic tumor activity is often marked and intense and it is easier to evaluate than changes in tumor shrinkage and density measured on CT. PET may also be useful when morphological findings are unclear, treatment efficacy uncertain or when progression is identified on CT scan, especially when these findings do not agree with clinical data. PET and CT are complementary and hybrid PET/CT systems have been shown to be useful in GIST. PET may be proposed for the assessment of treatment response in prospective studies with imatinib or other molecules. In patients with GIST, FDG-PET should be performed based on a pluridisciplinary decision.