Comparison of PET, CT, and dual-modality PET/CT imaging for monitoring of imatinib (STI571) therapy in patients with gastrointestinal stromal tumors.
This study was implemented to compare the value of PET, CT, and dual-modality PET/CT imaging for assessing gastrointestinal stromal tumor (GIST) response to imatinib therapy.


METHODS
Twenty patients with histologically proven GIST underwent (18)F-FDG PET/CT imaging before and 1, 3, and 6 mo after the start of imatinib therapy. Separate PET and CT datasets, side-by-side PET and CT datasets, and fused PET/CT images were evaluated according to World Health Organization, Response Evaluation Criteria in Solid Tumors, and European Organisation for Research and Treatment of Cancer criteria for therapy response. Hounsfield units (HU) were assessed on CT images. A mean follow-up period of 381 +/- 134 d served as the standard of reference.


RESULTS
The numbers of lesions detected in all patients were 135 with PET, 249 with CT, 279 on side-by-side evaluation, and 282 on fused PET/CT images. Tumor response was correctly characterized in 95% of patients after 1 mo and 100% after 3 and 6 mo with PET/CT. PET and CT images viewed side by side were correct in 90% of patients at 1 mo and 100% at 3 and 6 mo. PET accurately diagnosed tumor response in 85% of patients at 1 mo and 100% at 3 and 6 mo. CT was found to be accurate in 44% of patients at 1 mo, 60% at 3 mo, and 57% at 6 mo. HU were found to decrease by at least 25% in 12 of 14 responders after 1 mo.


CONCLUSIONS
Tumor response to imatinib should be assessed with a combination of morphologic and functional imaging. Image fusion with combined PET/CT can provide additional information in individual cases when compared with side-by-side PET and CT.
Antoch
Gerald
G
Department of Diagnostic and Interventional Radiology, University of Essen, Essen, Germany. gerald.antoch@uni-essen.de
Kanja
Jörg
J
Bauer
Sebastian
S
Kuehl
Hilmar
H
Renzing-Koehler
Katrin
K
Schuette
Jochen
J
Bockisch
Andreas
A
Debatin
Jörg F
JF
Freudenberg
Lutz S
LS
D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001549:Benzamides; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000188:drug therapy*; D006801:Humans; D000068877:Imatinib Mesylate; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000627:therapeutic use*; D011379:Prognosis; D011743:Pyrimidines / Q000627:therapeutic use*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017154:Stromal Cells / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology; D013382:Subtraction Technique; D014055:Tomography, Emission-Computed / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate