Relationship between FDG uptake and the pathological risk category in gastrointestinal stromal tumors.

Purpose: To evaluate (18)F-fluorodeoxyglucose (FDG) uptake and the pathological risk category of gastrointestinal stromal tumors (GISTs), and to investigate the possibility of determining the pathological risk category by positron emission tomography/computed tomography (PET/CT).

Patients And Methods: We undertook 29 PET/CT studies in 20 patients with GISTs. Eleven of the 20 patients underwent PET/CT prior to therapy, with three of these also undergoing follow-up PET/CT after operation or imatinib therapy.

Results: All eleven lesions imaged before treatment were FDG-positive on PET/CT. Seven of these eleven primary lesions were categorized as high risk and the other four primary lesions were categorized as low or intermediate risk. There was a significant difference between the maximum standardized uptake value (SUVmax) of the primary lesions categorized as high risk (11.8±3.15) and that of the primary lesions categorized as low and intermediate risk (2.88±0.47) (p<0.001). Recurrent tumors were also shown as FDG-positive.

Conclusion: Primary GISTs and recurrent tumors can be detected by PET/CT. Our study suggests that the degree of FDG uptake is a useful indicator of risk category. In addition, PET/CT is probably useful for follow-up examinations of GIST after operation or imatinib therapy. J. Med. Invest. 57: 270-274, August, 2010.