ESTRO 2025 - Abstract Book

S2763

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

1360

Digital Poster Dosimetric improvements in prostate radiotherapy after clinical implementation of RapidPlan Mads Høyrup Brincker, Lars Merring-Mikkelsen Department of Medical Physics, Oncology, Aalborg University Hospital, Aalborg, Denmark Purpose/Objective: To evaluate the dosimetric improvements in prostate cancer treatment plans after clinical implementation of RapidPlan as a knowledge-based planning (KBP) tool. Material/Methods: 86 prostate cancer treatment plans were analyzed: 43 plans created with RapidPlan and 43 without. All plans were prescribed 78 Gy to PTV1 and 56 Gy to PTV2, used 7-field IMRT with identical field configuration, and were calculated using Eclipse with AAA version 16.1.0. Target and Organs At Risk (OAR) delineation and dose constraints adhered to the Danish Prostate Cancer Group guidelines [1]. The RapidPlan model was developed using 60 previously treated clinical plans and validated with 10 new patients. The model incorporated Dose Volume Histogram (DVH) information from target structures and OARs (rectum, bladder, bowel bag, and femoral heads), providing planners with realistic DVH estimates based on past clinical practice. Target structures and OARs were evaluated using DVH analysis, and a Wilcoxon rank sum test was applied to compare the two groups. Results: Significant dosimetric improvements were observed in plans optimized with RapidPlan, as shown in Figure 1 and Table 1. The DVH comparison in Figure 1 demonstrates significant reductions in OAR doses, particularly for the rectum, where the mean dose decreased from 42.63 Gy to 34.97 Gy (p<7.41·10 ⁻ ⁸), and bladder from 49.03 Gy to 43.05 Gy (p<4.15·10 ⁻ ⁸). For the bowel bag, the DVH was significantly lower in the range 38.3-49.6 Gy but slightly higher between 56.5-57.8 Gy. Plan consistency was improved, particularly for rectum doses, where the standard deviation decreased from 6.63 Gy to 3.82 Gy. As shown in Table 1, target coverage was maintained, with PTV1 showing no significant difference at 95% dose coverage, though mean dose increased slightly (77.94 Gy to 78.14 Gy, p=0.002). PTV2 coverage at 95% showed a minimal decrease (99.97% to 99.78%).