ESTRO 2025 - Abstract Book

S2937

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

ESTRO 2025

Purpose/Objective: Historically, patients with brain metastases (BM) were irradiated with a whole brain radiotherapy (WBRT). New non WBRT methods include stereotactic radiosurgery (SRS and FSRT), hippocampal sparing WBRT or preoperative SRS. These modern techniques require adequate equipment with a renewal of treatment machines being planned in the long term, reflecting increasing numbers of patients and repeated RT for distal brain recurrence. The aim of this retrospective single-institution analysis is a descriptive analysis of the basic BM patient profile as a necessary prerequisite for adequate treatment machines renewal. Material/Methods: Total of 1461 consecutive brain tumor patients were irradiated between 2016 to 2021 at tertiary comprehensive cancer centre. Analysis of adult patients with BM focused on RT treatment planning procedure – group A: 2D planning (WBRT) and group B: 3D treatment planning using CT/MR simulation (non-WBRT). Results: Out of 1461 screened patients, 636 (43%) were irradiated with primary brain tumors (453 gliomas) and 825 (57%) with BM. From 2016 till 2021, there was anually 154 (27 after surgery), 132 (22 after surgery), 168 (19 after surgery), 186 (21 after surgery), 126 (13 after surgery) and 59 (12 after surgery) BM patients. Total of 470 patients (470/825; 57%) were treated based on 2D treatment planning (WBRT technique, most commonly prescribed dose 30Gy in 10 fractions or 20Gy in 5 fractions) and 355 (355/825; 43%) were treated using 3D treatment planning on CT simulator with or without pre-treatment planning MRI. The percentage of patients treated by modern non-WBRT techniques increased by years: 30%, 40%, 45%, 39%, 45%, 86%. The most common primary diagnosis was lung cancer (40%; 203 NSCLC and 124 SCLC), followed by breast (165; 20%), melanoma (92; 11%) and kidney (59; 7%). In total, median overall survival (OS) was 3.0 months (95% CI 2.7-3.3) with 1-year OS 20.6% (95% CI 17.5-23.9%). Corresponding values for group A were 1.9 (1.7-2.1) months and 7.1 (4.7-10.0)% and for group B 7.0 (5.9-8.8) months and 39.4 (33.3 45.4)%. OS did not differ in respect to the treated year. Conclusion: Internal registries of BM patients are essential for responsible planning of treatment machine renewal but also for the implementation of new radiation neuroprotective techniques. The increasing number of stereotactic radiotherapy including reirradiations, especially combined with targeted therapy or immunotherapy, will continue to increase the demands for accurate differential diagnosis of postradiotherapy MRI changes with increasing emphasis on the use of radiomic methods in the evaluation of post-treatment MRI. Supported by NU22-03-00159.

Keywords: radiotherapy, brain metastases, radiomics

4536

Digital Poster The dosimetric impact of waiting times for postoperative radiotherapy in the treatment of breast cancer Hela Ayouni 1,2 , Bilel Daoud 3 , Yosra Kochlef 2 , Lotfi Ben Salem 4 , Semia Zarraa 2 , Chiraz Nasr 2 1 Medical physics, Higher Institute of Medical Technology of Tunis, Tunis, Tunisia. 2 Radiotherapy oncology, Institute Salah Azaiez, Tunis, Tunisia. 3 Imaging physics research, MD anderson cancer center, Texas, USA. 4 Medical physics, Institute Salah Azaiez, Tunis, Tunisia Purpose/Objective: In the treatment of most cancers, waiting times for postoperative radiotherapy (RT) should be as short as reasonably achievable. In the context of breast cancer (BC), various trials have reported that delayed initiation of RT has a negative impact on survival and local relapse [1,2]. The aim of this study was to assess whether there is a relationship between delay and dosimetric outcomes.