Gastrointestinal stromal tumors are the most common mesenchymal tumors of the gastrointestinal tract (GIT). About 5000 to 6000 new cases of GISTs are diagnosed in the United States annually. Response to conventional chemotherapeutic agents and radiation therapy is disappointing. Early experience with the tyrosine kinase inhibitor, STI-571 (Gleevec, imatinib mesylate), has been extremely encouraging and it is now an FDA approved treatment.
The role pf PET is udner investigation. Positron emission tomographic scanning with the radiotracer 18F-FDG can reveal early functional changes in tumor glucose metabolism that appear to correlate closely with metabolic response to imatinib mesylate. When compared with CT alone, PET with FDG and PET/CT provided valuable additional information about the extent and metabolic activity of the disease process. The response to drug therapy could be shown as early as 24 hours after completion of a therapeutic regimen.Though very promising, the number of reporteds and the number of published papers is too small to definitely assess sensitivity of PET and PET/CT in evaluating GIST response, as this malignancy is rare. A larger, multicenter study is required.
Antoch G, Kanja J, Bauer S, et al. Comparison of PET, CT, and dual-modality PET/CT imaging for monitoring of imatinib (STI571) therapy in patients with gastrointestinal stromal tumors. J Nucl Med.2004;45:357-365.
Van den Abbeele AD, for the GIST Collaborative PET Study Group. F18-FDG-PET provides early evidence of biological response to STI571 in patients with malignant gastrointestinal stromal tumors [abstract]. Proc Am Soc Clin Oncol. 2001;20:362a; Abstract 1444.