Evaluation of Dual–Time-Point 18F-FDG PET for Staging in Patients with Lung Cancer

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Abstract
18F-FDG PET is increasingly used for lung cancer; however, some insufficient results have been reported. The purpose of this study was to evaluate the efficacy of dual–time-point 18F-FDG PET for staging lung cancer and for differentiating metastatic from nonmetastatic lung cancer lesions. Methods: One hundred fifty-five lung cancer patients with known or suspected mediastinal and hilar lymph node involvement or distant metastases underwent whole-body 18F-FDG PET at 2 time points: scan 1 at 60 min (early imaging) and scan 2 at 180 min (delayed imaging) after 18F-FDG injection. 18F-FDG PET findings of nodal and distant metastases were evaluated using conventional imaging, clinical follow-up findings, and the results of autopsy or biopsy. Results: A total of 580 lesions (155 primary lesions, 315 metastatic lesions, and 110 nonmetastatic lesions) were used for analysis. A closer correlation between the primary lesions and metastases was observed for the retention index (RI) standardized uptake value (SUV) than for early and delayed SUV. There was no relationship between the RI SUV results of primary lesions and those of nonmetastatic lesions. The RI SUV of metastatic lesions was approximately 0.5–2 times the RI SUV of primary tumors. We found that the accuracy of 18F-FDG PET was improved when RI SUV was used for detecting lymph node and distant metastases, because of the significant improvement in specificity relative to early and delayed SUV. Conclusion: RI SUV raised the accuracy for diagnosis of metastases and was superior to early and delayed imaging in terms of differentiating malignancy from nonmetastatic uptake.

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