e15620 Background: To determine whether FLT PET/CT can detect regional lymph nodes metastases in untreated thoracic esophageal squamous cell carcinoma. In view of the reported high sensitivity of FDG PET/CT for the evaluation of thoracic nodules of esophageal carcinoma, we additionally performed FDG PET/CT for direct comparison with that of FLT. Methods: From March 2008 to December 2008, 18 patients with thoracic esophageal squamous cell carcinoma underwent dual-tracer PET/CT examinations before surgery. The results of reviewing side-by-side FDG PET/CT and FLT PET/CT images for the diagnosis of locoregional lymph node metastases were compared prospectively in relation to pathologic findings. The PET images were visually inspected with the maximum standardized uptake value (SUVmax) determined from a circular region of interest (ROI) over the entire lesion. The differential threshold for malignancy was set as SUVFDG≥2.5, and SUVFLT≥1.4, respectively. Results: All patients underwent esophagectomy and lymphadenectomy, and pathologic examination confirmed nodes positive for metastasis in 14 patients and 42 of 344 excised nodes. The uptake of FDG (median SUVmax, 5.59; range, 2.5–10.6) in locoregional lymph nodes metastasis was significantly higher than that of FLT (median SUVmax, 2.93; range, 1.6–4.6). There were 14 false positive nodes in FDG PET and only 3 in FLT PET, 7 false negative nodes in FDG PET, while 11 false negative nodes in FLT PET. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of FLT PET/CT were 73.81%, 99.01%, 95.93%, 91.18% and 96.45%, respectively, whereas those of FDG PET/CT were 83.33%, 95.36%, 93.90%, 71.43% and 95.36%, respectively. P values were 0.425, 0.014, 0.298, 0.055, and 0.541, respectively. Conclusions: FLT uptake in regional lymph node of esophageal carcinoma is significantly lower compared with FDG uptake.FLT PET has fewer false-positive findings compared with FDG PET. The specificity of FLT PET/CT is higher than that of FDG. We suggest that esophageal carcinoma N-staging need to combine FLT with FDG PET/CT images. No significant financial relationships to disclose.
PO-0859: Combined 18F-FDG and 18F-FLT PET/CT image characteristics to analyze esophageal squamous cell carcinoma stage
