ESTRO 2025 - Abstract Book

S1368

Clinical - Lung

ESTRO 2025

Material/Methods: We conducted a retrospective cohort study on locally advanced (stage III and IV) NSCLC patients with [ 18 F]FDG PET scans older than 3 weeks, in whom repeat [ 18 F]FDG PET imaging on the Quadra scanner was performed prior to start of (chemo-)radiotherapy. The effect of repeat imaging on TNM-staging changes was analyzed. The impact on TNM-stage progression and treatment was assessed using logistic regression and Wilcoxon Signed Rank tests, while adjusting for baseline clinical characteristics: patient performance (WHO), tumor location, tumor histology and mutation status. Results: We included 21 NSCLC patients with 22 tumors. The median time between the PET/CT scans was 58 days (8 weeks) [IQR: 50-71 days]. In 12 patients (54.5%), a higher overall TNM stage was detected. In 13 patients (59.1%) there was a N-stage increase and 15 patients (68.2%) had new nodal target volumes (while the N-stage remained the same). The new nodal involvement locations are shown below.

Moreover, 2 patients had metastasized disease, which resulted in either palliative irradiation or no irradiation. The bar chart shows the TNM stage changes in percentages.