Significant Benefit of Multimodal Imaging: PET/CT Compared with PET Alone in Staging and Follow-up of Patients with Ewing Tumors

¹ Department of Nuclear Medicine, University Hospital Münster, Münster, Germany
² Department of Clinical Radiology, University Hospital Münster, Münster, Germany
³ Department of Pediatric Hematology and Oncology, University Hospital Münster, Münster, Germany
⁴ Department of Medical Informatics and Biomathematics, University Hospital Münster, Münster, Germany

^* To whom correspondence should be addressed. E-mail: huvgerth{at}uni-muenster.de.

	Abstract

Hybrid PET/CT was compared with PET alone in the staging and restaging of patients with Ewing tumor to assess the benefit of the combined imaging technique. Methods: A total of 163 ¹⁸F-FDG PET/CT studies performed in 53 patients (age: range, 4–38 y; median, 16.5 y) with histopathologically confirmed Ewing tumor were evaluated retrospectively. All PET/CT studies included low-dose CT for attenuation correction; in 91 examinations, additional diagnostic chest CT was performed. PET and CT data were assessed independently by 2 nuclear medicine physicians and 2 radiologists, respectively. Finally, both datasets were fused by use of software and analyzed by all 4 reviewers (consensus reading). Each lesion was scored with a 5-point scale. Biopsy, imaging, or clinical follow-up served as a standard of reference. Receiver operating characteristic (ROC) analyses were performed to evaluate PET and PET/CT performance characteristics. To measure the abilities to detect and correctly localize tumor foci, localization ROC (L-ROC) curves were generated for PET. Results: A total of 609 lesions were detected by PET alone. The hybrid PET/CT technique resulted in a change of score in 160 of these lesions (26%): higher scores in 23 lesions (4%) and lower scores in 137 lesions (23%). In 49 lesions detected by PET (8%), the localization had to be changed after image fusion. Additionally, 124 (21%) more lesions were found by PET/CT than by PET alone, resulting in a total of 733 lesions. As determined by lesion-based analysis, the sensitivity, specificity, and accuracy of PET were 71%, 95%, and 88%, respectively; the corresponding values for the hybrid PET/CT technique were 87%, 97%, and 94% (P < 0.0001). The areas under the curve in the ROC analysis were 0.82 for PET and 0.92 for PET/CT (P < 0.0001), and that in the L-ROC analysis was 0.66 for PET. Conclusion: PET/CT is significantly more accurate than PET alone for the detection and localization of lesions and improves staging for patients with Ewing tumor. The hybrid technique is superior to PET alone in terms of sensitivity, specificity, and accuracy, mainly because of the detection of new lesions.

Key Words: PET, PET/CT, Ewing tumor, sarcoma; ROC analysis

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