S880
Clinical - Mixed sites & palliation
ESTRO 2026
prospective studies are warranted to refine dose–time parameters and identify optimal candidates. References: 1. Marples, B., & Collis, S. J. (2008). Low-dose hyper- radiosensitivity: past, present, and future. International journal of radiation oncology, biology, physics, 70(5), 1310–1318. Keywords: re-irradiation, low-dose hyper- radiosensitivity Digital Poster 2269 Single-isocenter non-coplanar stereotactic radiosurgery for brain metastasis in Hong Kong: long term outcomes and prognostic factors Philip Y Wu 1 , Elki SN Cheung 1 , Frederick CH Law 2 , William WL Wong 1 , Nelson TC Fung 2 1 Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong. 2 Department of Medical Physics, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong Purpose/Objective: Stereotactic radiosurgery (SRS) is the current standard of care for limited brain metastasis (BM), and suitable patients with extensive disease1-2. Considerable heterogeneity exists in tumour characteristics, case selection and SRS techniques in real-world settings. Single-isocenter linear accelerator (linac)-based SRS allows efficient off-axis irradiation of multiple targets simultaneously3, and has been increasingly adopted. The study evaluates on clinical outcomes of single- isocenter SRS for BM in a contemporary Chinese cohort. Material/Methods: Consecutive patients with MRI-diagnosed BM of solid tumour primary who received single-isocenter non- coplanar linac-based SRS between February 2020 and January 2025 were included in this retrospective study. SRS in combination with whole brain radiotherapy was not permitted. The primary outcome was local control (LC). Secondary outcomes included distant intracranial failure-free survival (DFFS) and overall survival (OS), analysed in patients who received first-episode SRS. Relevant prognostic factors for oncological outcomes were evaluated. SRS-related toxicity was graded by Common Toxicity Criteria for Adverse Events (version 5.0). Results: 146 courses of SRS for 301 treated lesions were identified in 121 patients. 114 courses were first- episode SRS while 32 courses were subsequent. Primary disease was non-small cell lung cancer (NSCLC) in 77%, and among them 62% had oncogenic
metastatic epidural spinal cord compression: Final results of the SCORE-2 trial (ARO 2009/01). J Clin Oncol 2016;34(6):597-602.4. Castro JR, Chen A, Kamrava M, Larson DA, Ning S, Pouliot J, et al. Quality indicators in radiation oncology. Lancet Oncol 2008;9(6):559-568. Keywords: follow-up, quality indicator, quality of life Digital Poster 2031 Hyper-radiosensitivity-guided sequencing radiotherapy in re-irradiation or radioresistant patients Shao-Wei Chiang, Yu-Wei Lin Department of Radiation Oncology, Kaohsiung Veterans General Hospital, Kaohsiung City, Taiwan Purpose/Objective: Low-dose hyper-radiosensitivity (HRS) may enhance cell-kill at doses < 0.5 Gy. Preclinical data suggest that a very low “priming” dose immediately prior to a standard fraction may improve tumor control. We evaluate the early clinical outcomes of treatment efficacy and acute toxicity of HRS-guided sequencing radiotherapy incorporating a 0.25 Gy priming dose in re-irradiation or radioresistant cases. Material/Methods: Patients treated with HRS-guided sequencing radiotherapy at a single institution from June 2024 to June 2025 were retrospectively reviewed. A 0.25 Gy priming dose was delivered seconds before each fraction (1.55–4.25 Gy) using electrons or VMAT/IMRT photons. Treatment followed conventional daily fractionation. Total doses corresponded to EQD ₂ 40– 65 Gy. The primary endpoint was clinical response using RECIST 1.1 and the secondary endpoints included symptom relief and acute toxicity graded by CTCAE v5.0. Results: A total of 7 patients were treated with HRS-guided sequencing radiotherapy, including 6 re-irradiation cases. The median follow-up after radiotherapy was 4 months (range, 2–12 months). Four patients were head and neck cancer, two were breast cancer and one Merkel cell carcinoma of cheek. Of the 7 patients, 6 patients (85.7%) achieved at least a partial response or symptom relief after HRS-guided sequencing radiotherapy. No acute grade ≥ 3 toxicities occurred. Grade 1–2 dermatitis and mucositis were the most common events. Conclusion: HRS-guided sequencing with a 0.25 Gy priming dose was feasible and safe. Preliminary outcomes showed encouraging efficacy in challenging cases of re- irradiation and radioresistant patients. Further
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