ESTRO 2025 - Abstract Book

S3604

Physics - Quality assurance and auditing

ESTRO 2025

applied trial-defined dose-volume constraints for target volumes and OAR and generated a standard plan (SP) and a dose-escalated plan (EP) for five distributed cases. All plans were exported to a central treatment planning system. Level of dose-escalation and doses to OAR were reported and presented as medians and range [minimum maximum]. Doses to OAR for SPs and EPs were pairwise compared using the Wilcoxon signed rank test (significance if p<0.05). Results: Mean dose for the escalation (D mean ), checked locally, for the EPs was 79.5Gy [76.9Gy-80.0Gy] and 75.9Gy [68.3Gy 80.0Gy] for GTVt and GTVn, respectively. The large variability in GTVn doses between cases was due to the GTVn localization close to OAR. There were three deviations from dose-limiting constraints, mandatory to fulfill: one for the heart and two for esophagus, for different cases and centers. There was a significant (p=0.001) difference in mean lung dose (MLD) of 13.4Gy [6.9Gy-17.0Gy] for SPs and 14.1Gy [7.0Gy-17.6Gy] for EPs. There was no significant (p=0.187) difference between SPs and EPs for mean heart dose (MHD) of 6.8Gy [1.9Gy-22.3Gy] and 7.3Gy [1.8Gy 20.8Gy], respectively. Boxplots of D mean , MLD and MHD are presented in Figure 2, and show that the variation in dose distribution between centers was low, but largest for MHD. Conclusion: Inhomogeneous dose-escalation up to 80Gy/40fx/10week for GTVt and GTVn in patients eligible for the trial seams feasible. The dose-escalation can be performed respecting the OAR constraints in the upcoming NIELS trial.