Clinical usefulness of dual-time FDG PET-CT in assessment of esophageal squamous cell carcinoma

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.