S988
Clinical - Oligometastatic cancer
ESTRO 2026
Keywords: oligometastatic colorectal cancer, SBRT, repeated
24 months, the cumulative incidence of LF was 46.5% (95% CI, 20.5–69.0%) for SBRT+ MASS versus 16.6% (95% CI, 11.4–22.6%) for SBRT, this difference remained significant in the matched cohort (P < 0.001). Death as a competing risk also differed significantly between cohorts (P < 0.001). Conclusion: Patients treated with MASS followed by SBRT had higher LF compared with SBRT alone, with competing risk of death also differing between cohorts. This likely reflects more advanced, complex disease and technical challenges intrinsic to postoperative SBRT, difficult to adjust for even through matching. Future studies incorporating detailed dosimetric analyses and recurrence mapping are warranted. Keywords: Spine SBRT, Spinal metastases Digital Poster 4332 MR-guided adaptive stereotactic radiotherapy for oligometastatic prostate cancer: clinical and radiographic outcomes Levi Burns 1 , Iymad Mansour 2 , Jeff Winter 2 , Amanda Moreira 3 , Peter Chung 1 , Andrew Bayley 1 , Aruz Mesci 1 , Charles Catton 1 , Badr Id Said 1 , Rachel Glicksman 1 , Andrew McPartlin 1 1 Radiation Oncology, Princess Margaret Cancer Centre, Toronto, Canada. 2 Medical Physics, Princess Margaret Cancer Centre, Toronto, Canada. 3 Radiation Therapy, Princess Margaret Cancer Centre, Toronto, Canada Purpose/Objective: MR-guided adaptive radiotherapy leverages superb soft tissue contrast visualization to adapt to daily target and OAR changes. When applied to SBRT, MR- SBRT is hoped to achieve local control associated with SBRT [1,2] with improved toxicity. We assess outcomes for prostate cancer oligometastasis (OM) patients treated with MR-SBRT on a single-centre prospective
Digital Poster 4273
Definitive Stereotactic Body Radiotherapy Versus Minimal Access Separation Surgery plus SBRT for Spinal Metastases: A Propensity-Matched Analysis Enrique Gutierrez-Valencia 1 , Adeodatus Vito Nicanor 1 , Mehran Nasralla 2 , Jane Jomy 1 , Anna Theresa Santiago 1 , Hiba Othman 1 , David Shultz 1 , Roger Smith 2 , Eric Massicotte 3 , Michael Yan 1 1 1. Radiation Medicine Program, Princess Margaret Cancer Centre & University of Toronto, Toronto, Canada. 2 2. Department of Neuroradiology, , University Health Network & University of Toronto, Toronto, Canada. 3 3. Department of Neurosurgery, University of Toronto & Toronto Western Hospital, Toronto, Canada Purpose/Objective: Stereotactic body radiotherapy (SBRT) is a safe and well-established technique for the treatment of spinal metastases. We sought to compare local failure (LF) and toxicity outcomes in patients treated with minimal access surgical resection (MASS) plus SBRT versus SBRT alone. Material/Methods: This is a retrospective observational study of patients with spinal metastases treated with SBRT between 2015 and 2024. Overall survival (OS) was estimated using the Kaplan-Meier method with Log-rank test. LF was assessed using cumulative incidence analysis with Gray’s test and accounting for death as the competing risk. A sensitivity analysis for LF was performed using a matched sample generated by one-to-one nearest neighbor propensity score matching based on radioresistance, Bilsky grade, and biologically effective dose (BED). Results: A total of 145 patients were included: 124 received SBRT alone and 21 received SBRT following surgery, comprising 207 treated lesions (182 SBRT, 25 SBRT+MASS). Median age was 66 years old (range, 17– 85) in the SBRT cohort and 55 years (range, 40–72) in the SBRT+MASS cohort (P = 0.007). Bilsky scores for the entire cohort were 1 in 160 (77.3%) lesions and 2–3 in 47 (22.7%). In the SBRT group, 146 patients (80.2%) had a Bilsky score of 1: 1A in 42 (23.1%), 1B in 62 (34.1%), and 1C in 42 (23.1%), while 36 patients (19.8%) had scores of 2–3. In the SBRT+MASS group, 14 patients (56.0%) had a Bilsky score of 1: 1B in 4 (16%) and 1C in 10 (40%), whereas 11 patients (44.0%) had scores of 2–3 (P = 0.014). Cumulative incidence of LF was significantly higher in the SBRT+ MASS group compared with SBRT alone (Gray’s test, P < 0.001). At
REB-approved study. Material/Methods:
The cohort includes prostate OM patients receiving MR-SBRT with minimum one year of follow-up. Analysis endpoints include biochemical response, local and distant radiographic progression, and toxicity, reported with descriptive statistics. Local control was defined as absence of radiographic progression of a treated OM. Patient-reported quality of life (QoL) outcomes were collected serially with the EORTC-QLQ- C30 questionnaire. Results: Patient characteristics and prescription doses are summarized in Table 1. 38 patients received 45 courses of MR-SBRT. Of 33 patients who were not upfront metastatic and received curative-intent treatment, 21/33 (63.6%) received MR-SBRT as their
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