Long-term prognostic value of 18F-FLT PET/CT versus 18F-FDG PET/CT in locally advanced oesophageal squamous cell carcinoma: a prospective study

Background Accurate prognostication in locally advanced oesophageal squamous cell carcinoma (LA-ESCC) remains a significant clinical challenge. This prospective study aimed to compare the predictive value of fluorine-18 fluorodeoxyglucose ( 18 F-FDG) and fluorine-18 fluorothymidine ( 18 F-FLT) positron emission tomography/computed tomography (PET/CT) regarding long-term clinical outcomes. Methods Between June 2018 and July 2019, 31 patients with LA-ESCC were prospectively enrolled and underwent both 18 F-FDG and 18 F-FLT PET/CT scans prior to or during initial therapy. Quantitative parameters, including maximum standardized uptake value (SUV max ), minimum SUV (SUV min ), mean SUV (SUV mean ), tumour metabolic volume (MTV), total lesion glycolysis (TLG), and total lesion 18 F-FLT expression (TLT), were measured for primary tumours and regional lymph nodes. Progression-free survival (PFS) and overall survival (OS) were analysed using Cox univariate regression, receiver operating characteristic (ROC) curve analysis, and Kaplan-Meier survival estimates. Results In 18 F-FLT PET/CT, primary tumour parameters (SUV max , SUV mean , TLT) and all lymph node parameters significantly distinguished between favourable and poor PFS groups (all P <0.05). Primary tumour SUV max , SUV mean , and all lymph node parameters demonstrated a negative correlation with both PFS and OS. Specifically, lymph node SUV max (PFS: hazard ratio (HR)=1.65, 95% confidence interval (CI):1.23–2.19, P =0.002; OS: HR = 1.81, 95% CI:1.29–2.55, P <0.001) and SUV mean showed strong predictive value. In contrast, for 18 F-FDG PET/CT, only lymph node MTV differed significantly between PFS groups (P =0.03), with no parameters showing significant prognostic correlation. ROC analysis indicated that 18 F-FLT lymph node SUV max and SUV mean yielded the highest predictive accuracy for PFS (area under the curve (AUC): 83.8% and 84.2%, respectively) and OS (AUC: 79.3% for both). Conclusions 18 F-FLT PET/CT may offer superior prognostic value compared to 18 F-FDG PET/CT for long-term survival prediction in LA-ESCC. Parameters derived from metastatic lymph nodes, particularly SUV max and SUV mean , may serve as potential biomarkers for poor clinical outcomes, independent of imaging timing.