Purpose: We conducted this study to investigate the value of the dual-time 2-[ 18F]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography-computed tomography (PET-CT) in assessment of the primary tumor, loco-regional lymph node and distant metastasis in patients with esophageal squamous cell carcinoma. Methods: Twenty-six patients with histologically proved esophageal squamous cell carcinoma underwent dual-time FDG PET-CT before radical surgery. The standardized uptake values (SUV max) were obtained including early SUV max and delayed SUV max, respectively. The retention index (RI) was also calculated. The results were evaluated retrospectively according to the final pathologic findings. Four diagnostic criteria including (1) early SUV max ≧ 2.5 alone, (2) RI ≧ 10% alone, (3) a combination of early SUV max ≧ 2.5 and RI ≧ 10%, and (4) a combination of early SUV max ≧ 2.5 or RI ≧ 10% were used for differentiating malignancy from a benign lesion, respectively. Results: The sensitivity of FDG PET-CT in detecting the primary tumor with combination of early SUV max ≧ 2.5 or RI ≧ 10% was 96.2%. It was statistically significantly higher than the results using the other three criteria (p <0.0001). For loco-regional lymph node detection, there was no significant difference among the 4 criteria. For distal metastases, the significantly higher specificity (100%) was found when using combination of early SUV max ≧ 2.5 and RI ≧ 10% or using early SUV max ≧ 2.5 alone than using the other two criteria (p = 0.0058). With regard to accuracy, no significant correlations were observed among primary tumor, loco-regional lymph nodes and distant metastasis (p > 0.05). Conclusion: The preliminary result of this study demonstrated that dual-time point FDG PET-CT had limited value in detection of primary tumor and loco-regional lymph nodes metastasis. For the distant metastasis, the sensitivity and specificity would be improved if RI ≧ 10% is used as a supplemental criterion. Efforts should be made to improve the ability of the dual-time FDG PET-CT technique to assess primary tumor and loco-regional lymph nodes metastasis.
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