S1514
Interdisciplinary - Quality assurance and risk management
ESTRO 2026
after breast-conserving surgery. Material/Methods:
2014 Jul 8. doi:10.1120/jacmp.v15i4.4873 Keywords: breast, radiotherapy, recontouring,
A retrospective analysis included 168 patients treated with adjuvant radiotherapy after breast-conserving surgery at KBC Rijeka between January 2025. and October 2025. Patient data were collected from medical records and included demographic information, type of surgical procedure, surgical complications, number of isolated lymph nodes, and reception of neoadjuvant and adjuvant chemotherapy. Three temporal intervals were evaluated: the time from surgery to CT simulation (interval 1), the time from CT simulation to the first radiotherapy fraction (interval 2), and the sum of the two (interval 3). The necessity of recontouring was assessed based on visual evaluation of anatomical changes and volume alterations noted on CBCT. The study evaluated the need for recontouring and replanning during the radiotherapy course and investigated potential factors associated with this need. Results: This retrospective analysis revealed that recontouring was necessary in 10.7% of cases. Among patients requiring recontouring, the mean CTV decrease was 21.9 cm3, ranging from -193.7 to +240.4 cm3, indicating substantial anatomical variability. However, no statistically significant associations were found between recontouring necessity and surgical procedure type (p=0.543), lymph node count (p=0.379), receipt of neoadjuvant chemotherapy (p=0.234), receipt of adjuvant chemotherapy (p=0.779), or temporal intervals (interval 1: p=0.911; interval 2: p=0.965; interval 3: p=0.919). Conclusion: The lack of significant associations between recontouring necessity and the examined clinical factors suggests that anatomical changes requiring recontouring may be unpredictable based on readily available patient and treatment characteristics. These findings indicate that the decision to perform recontouring may not be predictable. References: 1. Kedar D, Nachum O, Zaretski A, Barnea Y. Prevalence of Breast Edema Following Conservative Breast Therapy in Israeli Patients. Isr Med Assoc J. 2025;27(8):515-519.2. Young-Afat DA, Gregorowitsch ML, van den Bongard DH, et al. Breast Edema Following Breast-Conserving Surgery and Radiotherapy: Patient-Reported Prevalence, Determinants, and Effect on Health-Related Quality of Life. JNCI Cancer Spectr. 2019;3(2):pkz011. Published 2019 Apr 16. doi:10.1093/jncics/pkz011.3. Klepper R, Höfel S, Botha U, Köhler P, Zwicker F. Dosimetric effects of swelling or shrinking tissue during helical tomotherapy breast irradiation. A phantom study. J Appl Clin Med Phys. 2014;15(4):382–391. Published
Proffered Paper 2298 In vivo dose measurements evaluation over time as a quality indicator in radiotherapy Cristina Anson Marcos 1 , Ania Sindermann i Muñoz 2 , Jaime Pérez-Alija Fernández 1 , Pedro Gallego Franco 1 , Natalia Tejedor Aguilar 1 , Helena Vivancos Bargalló 1 , Eva María Ambroa Rey 1,3 , Agustín Ruíz Martínez 1 , Marta Barceló Pagès 1 , Víctor Riu Molinero 1 , Alejandro Domínguez Perea 1 , Javier Roda García 1 , Pol Martínez Ramos 1 , Pablo Carrasco de Fez 1 , Nuria Jornet Sala 1 1 Medical Physics, Hospital Santa Creu i Sant Pau, Barcelona, Spain. 2 Physics, Universidad de Barcelona, Barcelona, Spain. 3 Medical Physics, Hospital del Mar, Barcelona, Spain Purpose/Objective: The aim of this study is to present the results obtained from in vivo dosimetry (IVD) at our center, used as a quality indicator for radiotherapy treatments over a 4- year period. Material/Methods: Patients undergoing breast, head and neck (H&N), pelvic, prostate, lung, and abdominal radiotherapy between 2021 and 2024 were selected. Treatments were delivered using three TrueBeam STx (Varian) equipped with aS1200 EPID, and included 3DCRT, IMRT, and VMAT techniques.2D transit IVD was performed using PerFractionTM (SunCHECK) on the first treatment fraction and once a week. Analysis was performed using local gamma analysis (20% threshold) 3%/3mm for H&N, 5%/5mm for pelvis, prostate and lung, and 5%/7mm for breast. Tolerance level was set at 90% for breast, and 95% for the rest of locations. A total of 39,465 images were analyzed. Whenever the GPR was out of tolerance, its cause was reported according to the classification shown in Figure 2The mean and variability (SD) of gamma passing rate (GPR) of all beams per year classified by treatment location was chosen as quality indicators. Results: Figure 1 shows GPR values for different treatment locations per year.
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