ESTRO 2025 - Abstract Book

S1747

Clinical – Upper GI

ESTRO 2025

450

Digital Poster The Long-term Prognostic Value of 18F-FLT Versus 18F-FDG PET in Patients with Locally Advanced Esophageal

Squamous Cell Carcinoma: A Prospective Study QIFENG WANG, WenYan Gao, Yi Wang, Lei Wu Radiation Oncology, Sichuan Cancer Hospital, Chengdu, China

Purpose/Objective: This prospective study was conducted to compare the prognostic value of 18F-fluorodeoxyglucose (18F-FDG) and 18F-fluorothymidine (18F-FLT) PET/CT in predicting long-term outcomes in patients with locally advanced esophageal squamous cell carcinoma (LA-ESCC). Material/Methods: A total of 31 patients diagnosed with LA-ESCC were enrolled and underwent both 18F-FDG and 18F-FLT PET/CT imaging at baseline, prior to initiating treatment. Parameters analyzed for each PET/CT modality included maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), minimum standardized uptake value (SUVmin), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and total lesion FLT expression (TLT) for both the primary tumor and any PET-positive lymph nodes. Cox proportional hazards models were used for univariate regression analysis to assess each parameter's predictive power for progression-free survival (PFS) and overall survival (OS). Receiver operating characteristic (ROC) curve analysis was further employed to identify optimal cut-off values for significant predictors. Kaplan-Meier survival curves were used to evaluate PFS and OS outcomes based on these cut-offs. Results: Among the imaging parameters derived from 18F-FLT PET/CT, lymph node SUVmean and SUVmax showed significant correlations with both PFS and OS (P < 0.05), while primary tumor SUVmean was a strong predictor for PFS (P < 0.001) and OS (P = 0.023). Similarly, primary tumor SUVmax was predictive for PFS (P = 0.003). In contrast, parameters from 18F-FDG PET/CT showed no statistically significant association with PFS or OS, suggesting a limited prognostic role for 18F-FDG PET/CT in this patient cohort. For 18F-FLT PET/CT, the optimal cut-off values for lymph node SUVmax and SUVmean (4.26 and 2.84, respectively) identified patients with lower uptake values as having a notably higher 2-year PFS (SUVmax: 80% vs. 19%, P = 0.00092; SUVmean: 80% vs. 19%, P = 0.00092) and OS (SUVmax: 80% vs. 38.1%, P = 0.0036; SUVmean: 80% vs. 38.1%, P = 0.0036). Additionally, significant differences were observed in the 18F-FLT PET/CT parameters of the primary tumor (excluding MTV and SUVmin) and lymph nodes between patients with PFS >10 months and those with PFS ≤10 months (P < 0.05 for all). Conclusion: The results demonstrate that 18F-FLT PET/CT offers superior prognostic utility over 18F-FDG PET/CT in predicting long-term outcomes for patients with LA-ESCC. The prognostic value of 18F-FLT PET/CT was unaffected by imaging timing, underscoring its robustness as a prognostic tool.

Keywords: 18F-FLT PET/CT Esophageal Carcinoma OS

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Digital Poster Liver SBRT in more than 4 fractions: local control and recurrence patterns Alizée Renan 1,2 , Nicolas Demogeot 1 , Marie Bruand 1 , Maria Jolnerovski 1 1 Oncology Radiotherapy, Institut de Cancérologie de Lorraine, Vandoeuvre les Nancy, France. 2 Faculté de médecine, Université de Lorraine, Nancy, France