ESTRO 2025 - Abstract Book

S3123

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

References: [1]Smolders,A. , Rivetti,L. , Vatterodt,N. , Korreman,S. , Lomax,A. , Sharma,M. , Studen,A. , Weber,D.C. , Jeraj,R. ,& Albetini , F.(2024).DiffuseRT: predicting likely anatomical deformations of patients undergoing radiotherapy.Physics in Medicine & Biology,69(15),155016.https://doi.org/10.1088/1361-6560/ad61b7 [2]Pastor-serrano,O. , Habraken,S. , Hoogeman,M. , Lathouwers,D. , Schaart,D. , Nomura,Y. , Xing,L. ,& Perkó , Z.(2023).A probabilistic deep learning model of inter-fraction anatomical variations in radiotherapy.Physics in Medicine & Biology,68(8),085018.https://doi.org/10.1088/1361-6560/acc71d

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Digital Poster Dosimetric impact of anatomical modifications and positioning with SGRT and IGRT patients treated for breast cancer using IMRT or VMAT Faten Ibrahim 1 , Mathilde Cuenin 2 , Claire Charra-Brunaud 2 , Jean-Christophe Faivre 2 , Vincent Marchesi 1 , Karine Gerard 1 1 Department of Medical Physics, Institut de Cancérologie de Lorraine, Nancy, France. 2 Department of Radiotherapy, Institut de Cancérologie de Lorraine, Nancy, France Purpose/Objective: To evaluate the robustness of the treatment workflow implemented in our institution, that includes the planning technique and the patient setup based on the use of the SGRT combined with a daily CBCT (“SGRT+CBCT”). A secondary goal was to determine if the CBCTs frequency could be decreased by assessing a “SGRT only” patient positioning. Material/Methods: 34 patients with left-sided breast cancer who received breast/chest wall irradiation without (group 1, n=20) or with (group 2, n=14) lymph nodes irradiation were included in this study. The prescribed dose was mainly 40Gy in 15 fractions for both groups. All patients were treated on a Halcyon linac equipped with the AlignRT SGRT system using VMAT or IMRT planning techniques. To evaluate the robustness of both set-up approaches (“SGRT+CBCT” and “SGRT only”), the original plan was recalculated on each daily CBCT and dosimetric parameters concerning CTV coverage (V95%) and dose to OARs (heart: D mean and V16Gy, left lung: D mean and V17Gy) were collected for each session. The average dose over all sessions was compared to the initial plan using a Wilcoxon statistical test. Results: Based on a total of 1044 dose recalculations, for the group 1, the breast/chest wall CTV coverage was met for 100% of the cases for both set-up methods. For the group 2, all lymph nodes CTVs were sufficiently covered for all cases with the “SGRT+CBCT” set-up, however, the breast/chest wall CTV V95%>95% condition was only respected for 10 cases out of 14, where an arm positioning imprecision was found. Concerning the OARs, all clinical goals were respected for groups 1 and 2 for both set-up modalities. Conclusion: In our institution, for patients treated for breast/chest wall only, SGRT followed by a daily CBCT proved to be a robust workflow in dosimetrical terms, allowing us to consider reducing the CBCT frequency (on another treatment machine). For the cases of breast/chest wall with lymph nodes irradiation, improvements in initial patient positioning, particularly for the arm was highlighted.

Keywords: SGRT, breast, robustness