Comparison of 18F-FLT and 18F-FDG PET/CT for lymph node staging in thoracic esophageal carcinoma

Objective: To compare the diagnostic value 18F-fluorothymidine (FLT) and 18F-fluorodeoxyglucose (FDG) PET/CT in detecting lymph node metastases of untreated thoracic esophageal carcinoma. Methods: Twenty-two patients with thoracic esophageal squamous cell carcinoma underwent both 18F-FLT and 18F-FDG PET/CT before surgery. The imaging results of the two modalities in detecting regional lymph node metastases were compared prospectively with the pathologic findings. The χ2-test was used with SPSS 13.0. Results: All patients underwent esophagectomy and lymphadenectomy. The metastatic lymph nodes were found in 16 patients, from which 47 of 424 excised nodes were positive by pathologic examination. False positive results were 14 while false negative 8 on 18F-FDG PET/CT. In contrast, false positive results were only 3 but false negative were 12 on 18F-FLT PET/CT. The sensitivity, specificity, accuracy, negative predictive value, and positive predictive value were 74.47% (35/47), 99.20% (374/377), 96.46% (409/424), 96.89% (374/386) and 92.11% (35/38) respectively for 18F-FLT PET/CT, whereas the corresponding values were 82.98% (39/47), 96.29% (363/377), 94.81% (402/424), 97.84% (363/371) and 73.58% (39/53) respectively for 18F-FDG PET/CT (χ2 = 0.572, 6.018, 1.017, 0.348, 3.852, P>0. 05, <0.05, >0.05, >0.05 and >0.05). Conclusions: Compared with 18F-FDG PET/CT, 18F-FLT PET/CT may be less sensitive but more specific for the detection of lymph node metastases of thoracic esophageal carcinoma. (authors)