The optimal threshold of 18F-FLT PET and 18F-FDG PET to estimate the length of gross tumor volume in patients with squamous cell carcinoma of the thoracic esophagus verified by pathological examination

Abstract

e15665 Background: To determine the optimal method of using 3-deoxy-3-18F-fluorothymidine (FLT) positron emission tomography (PET) to estimate gross tumor length in esophageal carcinoma, and compared with that of 18F- fluorodeoxyglucose(FDG) PET. Methods: Twenty patients with esophageal squamous cell carcinoma treated with radical surgery were enrolled and detected by FLT PET, eighteen of them underwent FDG PET scan. Gross tumor volumes (GTVs) were delineated using seven different methods with FLT PET: visual interpretation, standardized uptake value (SUV) 1.3, SUV 1.4, SUV 1.5, and 20% of maximum standard uptake value (SUVmax), 25% SUVmax,30% SUVmax, on FLT PET imaging, and three different methods with FDG PET: visual interpretation, SUV 2.5, and 40%SUVmax on FDG PET imaging. The length of tumors on FLT PET scan were measured and recorded as LFLTvis, LFLT1.3, LFLT1.4, LFLT1.5, LFLT20%, LFLT25%, and LFLT30%, and FDG PET scan were measured and recorded as LFDGvis, LFDG2.5, and LFDG40%, respectively, and compared with the length of gross tumor in the resected specimen measured by pathological examination (LPath). Results: The mean (±SD) LPath was 5.16±2.19cm. The mean LFLTvis, LFLT1.3, LFLT1.4, LFLT1.5, LFLT20%, LFLT25%, and LFLT30%were 5.17±2.40cm, 5.55±2.43cm, 5.17±2.41cm, 4.95±2.44cm, 5.82±2.23cm, 5.32±2.31cm, and 5.04±2.28cm, respectively. Compared with the LPath, the P value were 0.971, 0.045, 0.972, 0.255, 0.066, 0.644, and 0.714, respectively. The correlation coefficients were 0.952, 0.944, 0.959, 0.948, 0.763, 0.783, and 0.800, respectively. The mean LFDGvis, LFDG2.5, and LFDG40% were 5.41±2.27cm, 5.38±2.25cm, and 4.02±1.57cm, respectively. Compared with the LPath, the P value were 0.098, 0.085 and 0.000, respectively. The correlation coefficients were 0.984, 0.990 and 0.932, respectively. On FLT PET, LFLT1.4, and on FDG PET, L FDG2.5 seem more approximate to LPath. The difference between LFLT1.4 and LFDG2.5 was not significantly (P=0.442), the correlation coefficients was 0.960. Conclusions: An SUV cutoff of 1.4 on FLT PET, and an SUV cutoff of 2.5 on FDG PET, provided the closest estimation of GTV length in this study No significant financial relationships to disclose.