Using 18F-fluorodeoxyglucose positron emission tomography/computed tomography to estimate the length of gross tumor and involvement of lymph nodes in esophagogastric junction carcinoma.

OBJECTIVE:To determine the optimal approach for estimating the length of gross tumor and involvement of the lymph nodes with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in esophagogastric junction carcinoma (EGJC). The result was verified with pathologic examination. MATERIALS AND METHODS:Twenty patients with diagnosed and untreated EGJC were enrolled. The length of the gross tumor was measured using different approaches with PET/CT: Standardized uptake value (SUV) 1.5-5.5 in intervals of 1.0 and 10%-50% of maximum SUV (SUVmax) on 18F-FDG PET/CT in intervals of 10%. The results were expressed as L1.0-L5.0, and L10%-L50%, respectively. The pathological length of gross tumor (Lpath) was calculated based on the shrinkage ratio of primary tumor. The measurable lymph nodes were measured on PET/CT preoperatively, labeled during operation, and examined for pathology. RESULTS:Lpath was 6.87 ± 2.25 cm, L30% and L2.5 were 6.61 ± 1.76 cm and 7.56 ± 1.89 cm, respectively. L30% was closer to Lpath than other % SUVmax, L2.5 was closer to Lpath than other absolute SUV thresholds. The diagnostic performance of 18F-FDG PET/CT for lymph nodes was best at the cutoff SUV of 2.7, providing sensitivity of 70% and a specificity of 83.7% for detecting lymph node metastases. CONCLUSIONS:The tumor length with 30% SUVmax as the threshold was closest to the actual pathological length of EGJC. The diagnostic efficiency of 18F-FDG PET/CT was best at the cutoff SUVmax of 2.7 for detecting lymph node metastases in EGJC.