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

Abstract

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. 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. 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. 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.