Whole-body Tumor PET Imaging
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View second image(ct). Abdominal CT
View third image(pt). Whole-body Tumor PET Imaging 6 months after with imatinib mesylate (Gleevec)
Full history/Diagnosis is available below
There was a marked response to therapy with dramatic improvement in the FDG uptake in the gastric fundal mass as well as significantly decreased activity within multiple hepatic lesions (corresponding to cystic lesions seen on the CT scan obtained following Gleevec treatment). Mild activity persists within the gastric wall, with a few foci of increased activity in the liver just right of midline, likely corresponding to residual disease.
Histologically, the tumor can be composed of spindle cells, epithelioid cells, or a mixed cell population.
These tumors are characterized by mutations of the KIT proto-oncogene that lead to constitutive activation of its tyrosine kinase activity. This can, in turn, stimulate the proliferation of the GIST cells and may inhibit apoptosis. The KIT protein (CD117) can be detected by an immunohistochemical method, which enable pathologists to distinguish GISTs from other mesenchymal gastrointestinal tumors (1).
Imatinib mesylate, (Gleevec, also called STI571) is an FDA-approved drug used for the treatment of chronic myeloid leukemia and GIST. It is a tyrosine kinase inhibitor. The experience with this drug in the treatment of GISTs is very encouraging. Within 8 hours of initiating Gleevec therapy, changes in the tumors can be seen on FDG-PET, suggesting a rapid metabolic response in the tumor cells. Histological examination demonstrates that the some of the tumors undergo myxomatous change,leaving small pyknotic nuclei in an eosinophilic myxoid background after treatment(1-2).
This case demonstrate that Gleevec is very effective in the treatment of GISTs and that its effect can be monitored by FDG-PET.
1. Berman JJ, O'Leary TJ. Gastrointestinal Stromal Tumor (GIST) Workshop, April 2 and 3, 2001, NIH, Bethesda, MD. Gastrointestinal stromal tumor workshop. Human Pathology 2001;32:578-582.
2. Joensuu H, Roberts PJ, Sarlomo-Rikala M, et al. Effect of the tyrosine kinase inhibitor STI571 in a patient with a metastatic gastrointestinal stromal tumor. N Eng J Med. 2001; 344:1052-6.
View followup image(ct). Whole-body Tumor PET Imaging after therapy with Gleevec, 400 mg/day, for 6 months
References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Gasterointestinal System, Category:Neoplasm, Neoplastic-like condition)
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