S994
Clinical - Oligometastatic cancer
ESTRO 2026
is an analysis of the 3-year outcome data. Material/Methods:
Prospective data was supplemented for extended follow-up by retrospective retrieval from electronic patient records and imaging modules. CTCAE version 5.0 was used to grade suspected treatment-related grade ≥ 2 adverse events. Systemic progression, initiation of new systemic therapy, new metastasis directed therapy and local failure at treated sites were recorded. Analyses included Kaplan-Meier (KM) estimates of fracture and survival endpoints. Results: A total of 67 patients with 78 targets were treated with bone SABR and were included for analysis, Figure 1. Median follow-up time for treatment-related adverse events was 2.6 years and 4.0 years for overall survival. Kaplan–Meier overall survival estimates at 1, 2, and 3 years were 93%, 79% and 70%, respectively. Median progression-free survival was 27 months (95% CI: 8.5– 47 months). During follow-up, 9 patients sustained an in-field grade ≥ 2 fracture; 3 within 0–12 months (one grade 2 and two grade 3), 3 between 12–24 months (one grade 2 and two grade 3), and 3 after 24 months (one grade 2 and two grade 3). By location, grade 2 fractures were one spine, one pelvis, and one costa; grade 3 fractures were four spine and two pelvis. The 1-KM for Grade ≥ 2 fracture risk at 3 years was 18.3% (95% CI: 6.5–28.6%), Figure 2. None of the patients with a grade ≥ 2 fracture had died within 3 years after SABR. There were no known cases of radiation- induced myelopathy and no other grade 3+ events were recorded.
Conclusion: SABR for oligometastatic bone lesions showed appreciable long-term symptomatic fracture risk in the BONY-M trial, with no cases of radiation-induced myelopathy. Additional long-term prospective data are needed to identify and refine predictors of treatment - related skeletal events after oligometastatic bone SABR, to better inform treatment decisions and potential preventive measures. References: 1: Spindler, Nicklas Juel, et al. "Stereotactic Ablative Radiotherapy of Bone Metastases in an Oligometastatic Setting: One-year follow-up of the BONY-M Phase II Trial." International Journal of
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