Comparison among ¹⁸F-FDG uptake parameters for assessing the prognosis of esophageal squamous cell carcinoma.

Objectives: To compare the fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) parameters before neoadjuvant chemotherapy (NAC) for surgical resection and to investigate the useful prognostic factor in esophageal squamous cell carcinoma patients.

Methods: Our patient population consisted of 94 esophageal squamous cell carcinoma patients. (78 men and 16 women). The median age of our population was 67 years (range, 38-79). The maximum standardized uptake value (SUVmax), volumetric parameters (metabolic tumor volume (MTV), total lesion glycolysis (TLG)), SUVpeak and maximum SUV corrected for lean body mass (SULmax) were measured for primary lesion. The fixed cut off value (SUV2.5) were used to delineate the MTV. All continuous variables were dichotomized according to specific cut off values, and the optimal values were determined using ROC analyses and Youden index. The relationship between PET parameters and clinicopathological variables (age, gender, tumor location, clinical stage, residual tumor and adjuvant therapy after surgical resection) was investigated using Wilcoxon rant test. The Cox proportional hazard model was applied to evaluate the effects of PET parameters and clinicopathological variables while adjusting for potential confounding factors. Overall survival (OS) and disease free survival (DFS) were evaluated by Kaplan Meier method, and the difference in survival between subgroups was analyzed by log-rank test. A probability level of <0.05 was considered significant.

Results: The cut off value of SUVmax, SUVpeak, SULmax, MTV and TLG was 15.5, 12.0, 11.8, 29.5 and 212.0. The median duration of follow up was 61 months (range 3-94months). The number of disease recurrence and death after surgical resection was 41 events, and 43 patients were died. All PET parameters were associated with advanced clinical stage (SUVmax: P=0.013, SUVpeak: P=0.009, SULmax: P=0.013, MTV: P=0.001, TLG: P=0.001), and high MTV was significantly associated with residual tumor positive (P=0.032). With adjustment for several clinicopathological variables, Cox regression analysis showed that MTV was significantly associated with DFS and OS (DFS, hazard ratio (HR)=1.007, 95%confidential interval (CI) 1.003-1.011, P=0.002, OS, HR=1.006, 95%CI 1.002-1.009, P=0.025). However, TLG, SUVmax, SUVpeak and SUL max were not significant prognostic factors for DFS and OS (DFS, SUVmax: HR=0.995, 95%CI 0.93-1.065, P=0.885, SUVpeak: HR=1.001, 95%CI 0.926-10.8, P=0.981, SULmax: HR=0.998, 95%CI= 0.919-1.084, P=0.961, TLG: HR=1.000, 95%CI= 0.998-1.002, P=0.856, OS, SUVmax: HR=1.018, 95%CI= 0.964-1.075, P=0.528, SUVpeak: HR=1.026, 95%CI= 0.961-1.096, P=0.437, SULmax: HR=1.027, 95CI=0.963-1.096, P=0.414, TLG: HR=1.001, 95%CI= 0.999-1.003, P=0.364). On the Kaplan-Meier survival curves, the patients with MTV<29.5 showed significantly higher survival rate than those with MTV≧29.5 for DFS and OS (log-rank test: 5 years-DFS 76.3% vs 57.1%; P=0.038, 5 years-OS 65.8% vs 46.4%; P=0.043).

Conclusions: MTV is an independent significant prognostic factor for DFS and OS rather than SUVmax, SUVpeak, SULmax and TLG in esophageal squamous cell carcinoma patients undergoing NAC before surgical resection.