S990
Clinical - Oligometastatic cancer
ESTRO 2026
multidisciplinary approach makes it feasible to safely deliver ablative-dose radiotherapy. Our findings demonstrate that this technique achieves good short- term local control with acceptable toxicity, allowing for safe dose-delivery while respecting cumulative OAR constraints. MRgSABR is a non-invasive, effective alternative to surgery or palliation for these high-risk patients. References: [1] F. L. Schneiders et al., “Clinical outcomes of MR- guided adrenal stereotactic ablative radiotherapy with preferential sparing of organs at risk,” Clin. Transl. Radiat. Oncol., vol. 43, no. July, pp. 1–7, 2023, doi: 10.1016/j.ctro.2023.100680.[2] N. Andratschke et al., “European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation : definition , reporting , and clinical decision making”, doi: 10.1016/S1470-2045(22)00447-8. Keywords: Re-irradiation, MR-guided, SABR Oligometastatic Disease in Elderly Patients: Outcomes and Predictive Factors of Efficacy Antonio Marco Marzo 1 , Davide Franceschini 1 , Ruggero Spoto 1 , Luca Dominici 1 , Beatrice Marini 1 , Enrico Pozzo 1 , Stefano Tomatis 1 , Ciro Franzese 1,2 , Marta Scorsetti 1,2 1 Radiotherapy & Radiosurgery, Humanitas Research Hospital, Rozzano, Italy. 2 Biomedical Sciences, Humanitas University, Rozzano, Italy Purpose/Objective: Elderly patients with oligometastatic cancer usually have little therapeutic possibilities, therefore stereotactic body radiation therapy (SBRT) can be a valid option to improve local control and prevent disease progression. This study aims to assess efficacy outcomes and to identify possible predictive factors in a large cohort of old patients treated with SBRT. Material/Methods: Patients aged 80 years or more, treated with SBRT for a maximum of five metastatic lesions from various primary tumours, have been included. Primary endpoint were Local Progression Free Survival (LPFS), Systemic Therapy Free Survival (STFS), Progression Free Survival (PFS) and Overall Survival (OS). Potential predictive factors were analysed using univariate analyses (Kaplan–Meier, log-rank tests), using R. Results: Digital Poster 4627 Stereotactic Body Radiotherapy for
One patient had Grade 1 nausea. Retrospective dose accumulation analysis confirmed that cumulative EQD2 constraints for digestive OARs were respected. Dosimetric analysis demonstrated the critical value of adaptation. Without adaptation, the original plan would have violated OAR constraints in 55% of fractions. The online adaptive process reduced these violations to just 6%. Furthermore, adapted plans improved median PTV V95% coverage by 6.2% and increased the GTV D98% for all patients.
Conclusion: MR-guided adaptive SABR permits delivery of ablative adrenal re-irradiation, by leveraging real-time imaging and collaborative, on-table adaptive planning, this
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