Xiaojun Zhong

Using 18F-Fluorodeoxyglucose Positron Emission Tomography to Estimate the Length of Gross Tumor in Patients With Squamous Cell Carcinoma of the Esophagus

PURPOSE To determine the optimal method of using (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) to estimate gross tumor length in esophageal carcinoma. METHODS AND MATERIALS Thirty-six patients with esophageal squamous cell carcinoma treated with radical surgery were enrolled. Gross tumor volumes (GTVs) were delineated using three different methods: visual interpretation, standardized uptake value (SUV) 2.5, and 40% of maximum standard uptake value (SUV(max)) on FDG-PET imaging. The length of tumors on PET scan were measured and recorded as Length(vis), Length(2.5), and Length(40), respectively, and compared with the length of gross tumor in the resected specimen (Length(gross)). All PET data were reviewed again postoperatively, and the GTV was delineated using various percentages of SUV(max). The optimal-threshold SUV was generated when the length of PET matched the Length(gross). RESULTS The mean (+/-SD) Length(gross) was 5.48 +/- 1.98 cm. The mean Length(vis), Length(2.5), and Length(40) were 5.18 +/- 1.93 cm, 5.49 +/- 1.79 cm, and 4.34 +/- 1.54 cm, respectively. The mean Length(vis) (p = 0.123) and Length(2.5) (p = 0.957) were not significantly different from Length(gross), and Length(2.5) seems more approximate to Length(gross.) The mean Length(40) was significantly shorter than Length(gross) (p < 0.001). The mean optimal threshold was 23.81% +/- 11.29% for all tumors, and it was 19.78% +/- 8.59%, 30.92% +/- 12.28% for tumors >/=5 cm, and <5 cm, respectively (p = 0.009). The correlation coefficients of the optimal threshold were -0.802 and -0.561 with SUV(max) and Length(gross), respectively. CONCLUSIONS The optimal PET method to estimate the length of gross tumor varies with tumor length and SUV(max); an SUV cutoff of 2.5 provided the closest estimation in this study.

COMPARISON OF 18F-FLUOROTHYMIDINE AND 18F-FLUORODEOXYGLUCOSE PET/CT IN DELINEATING GROSS TUMOR VOLUME BY OPTIMAL THRESHOLD IN PATIENTS WITH SQUAMOUS CELL CARCINOMA OF THORACIC ESOPHAGUS

PURPOSE To determine the optimal method of using (18)F-fluorothymidine (FLT) positron emission tomography (PET)/computed tomography (CT) simulation to delineate the gross tumor volume (GTV) in esophageal squamous cell carcinoma verified by pathologic examination and compare the results with those using (18)F-fluorodeoxyglucose (FDG) PET/CT. METHODS AND MATERIALS A total of 22 patients were enrolled and underwent both FLT and FDG PET/CT. The GTVs with biologic information were delineated using seven different methods in FLT PET/CT and three different methods in FDG PET/CT. The results were compared with the pathologic gross tumor length, and the optimal threshold was obtained. Next, we compared the simulation plans using the optimal threshold of FLT and FDG PET/CT. The radiation dose was prescribed as 60 Gy in 30 fractions with a precise radiotherapy technique. RESULTS The mean +/- standard deviation pathologic gross tumor length was 4.94 +/- 2.21 cm. On FLT PET/CT, the length of the standardized uptake value 1.4 was 4.91 +/- 2.43 cm. On FDG PET/CT, the length of the standardized uptake value 2.5 was 5.10 +/- 2.18 cm, both of which seemed more approximate to the pathologic gross tumor length. The differences in the bilateral lung volume receiving > or =20 Gy, heart volume receiving > or =40 Gy, and the maximal dose received by spinal cord between FLT and FDG were not significant. However, the values for mean lung dose, bilateral lung volume receiving > or =5, > or =10, > or =30, > or =40, and > or =50 Gy, mean heart dose, and heart volume receiving > or =30 Gy using FLT PET/CT-based planning were significant lower than those using FDG PET/CT. CONCLUSION A standardized uptake value cutoff of 1.4 on FLT PET/CT and one of 2.5 on FDG PET/CT provided the closest estimation of GTV length. Finally, FLT PET/CT-based treatment planning provided potential benefits to the lungs and heart.

Dual-time-point FDG PET for the evaluation of locoregional lymph nodes in thoracic esophageal squamous cell cancer.

PURPOSE Compare dual-time-point and single-time 18F-FDG PET in the evaluation of locoregional lymph node metastases in patients with esophageal squamous cell cancer. Then assess the efficacy of dual-time-point PET in the diagnosis of such nodules. METHODS 34 patients with thoracic esophageal squamous cell cancer underwent dual-time-point PET before surgery. Semi-quantitative analysis was performed using the standardized uptake value (SUV), obtained from early and delayed images (SUVearly and SUVdelayed, respectively). The retention index (RI) calculated according to the equation: (SUVdelayed-SUVearly) x 100/SUVearly was assessed. Results were compared prospectively in relation to pathologic findings. RESULTS 71 of 354 resected nodal groups from 28 patients were confirmed positive by pathology. SUVearly of 2.5 and RI of 10 were chosen as arbitrary cutoffs for differentiating malignancy from benign, the sensitivity, specificity, accuracy, negative and positive predictive value of dual-time-point PET were 88.73% (63/71 nodal groups), 91.87% (260/283), 91.24% (323/354), 97.01% (260/268) and 73.25% (63/86) respectively, those of single-time were 76.06% (54/71), 85.16% (241/283), 83.33% (295/354), 93.41% (241/258) and 56.25% (54/96) respectively. P values were 0.047, 0.012, 0.002, 0.052 and 0.017 respectively, indicating remarkable differences in sensitivity, specificity, accuracy, and positive predictive value between dual-time-point and single-time PET. CONCLUSION Dual-time-point 18F-FDG PET has the potential for improving the sensitivity, specificity, accuracy and positive predictive value in the evaluation of locoregional lymph nodes in thoracic esophageal squamous cell cancer.