S931
Clinical - Mixed sites & palliation
ESTRO 2026
Material/Methods: Between 2018 and 2025, a cohort of 95 patients diagnosed with brain metastases, comprising a total of 124 lesions, was enrolled from two institutions. Treatments were delivered at two distinct centers: SRS using Gamma Knife LINAC, and HFSRT using TrueBeam LINAC. Fifty patients underwent SRS, receiving single doses ranging from 17 to 20 Gy, while 45 patients received HFSRT, with a total dose of 27 Gy administered in three fractions. Clinical efficacy was assessed in terms of local control (LC), overall survival (OS), and intracranial progression (IP). Late side effects, specifically radionecrosis (RN), was evaluated using serial MRI scans performed at standardized intervals following treatment.Kaplan–Meier survival analyses were generated using a custom R script to identify potential cut-off points for key clinical variables. Parameters including gross tumor volume (GTV), total radiation dose and concomitant systemic therapies were correlated with LC, OS, IP, and RN outcomes. Results: Kaplan–Meier analysis estimated a median OS of 17 months among deceased patients, consistent with contemporary prognostic benchmarks. No statistically significant differences were observed between the SRS and HFSRT groups in terms of OS or LC. Radionecrosis represented the main late adverse event, occurring in 22.1% of treated lesions, with a median onset of 11 months post-treatment. The incidence of RN was comparable across both treatment modalities, although higher-grade adverse events were more frequent among patients treated with SRS.Furthermore, patients receiving modern systemic therapies—particularly tyrosine kinase inhibitors (TKIs) and immunotherapy—demonstrated a statistically significant improvement in OS (p = 0.04). However, this subgroup also exhibited a tendency toward higher- grade radionecrosis, suggesting a possible synergistic but toxic interaction between high-dose irradiation and systemic agents. Conclusion: Both SRS and HFSRT demonstrated comparable efficacy in the management of brain metastases, supporting the use of either modality based on individualized clinical considerations. The observed interaction between high-dose focal irradiation and contemporary systemic therapies highlights a dual effect: enhanced overall survival coupled with an increased risk of late radiation-induced toxicity. These findings underscore the need for tailored therapeutic strategies balancing efficacy and safety in the era of combined modality treatments. Keywords: SRS, SRT, Brain
Mini-Oral 4988 Efficacy and safety of immune checkpoint inhibitors with high-dose RT in metastatic cancer: a systematic review and meta-analysis of randomized trials Syed Fahad Farooq 1 , Anand Swaminath 2,3 1 Faculty of Medicine, University of British Columbia, Vancouver, Canada. 2 Department of Radiation Oncology, Juravinski Cancer Centre, Hamilton, Canada. 3 Department of Oncology, McMaster University, Hamilton, Canada Purpose/Objective: Radiotherapy (RT) combined with immune checkpoint inhibitors (ICIs) has shown potential to enhance antitumor immune response, yet clinical outcomes remain inconsistent for managing metastatic cancer. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to identify, synthesize, and critically appraise the existing evidence on the efficacy and safety of ICIs with high- dose RT including stereotactic body radiotherapy (SBRT) in metastatic cancer patients. Material/Methods: According to PRISMA guidelines, we performed a systematic search of Embase, CENTRAL, and MEDLINE databases from inception to April 2024 for RCTs that compared ICI + high-dose RT/SBRT vs. ICI alone in metastatic solid tumor patients. We excluded studies that involved other systemic therapies (chemotherapy, hormone therapy, targeted therapy, etc.) or low- dose/palliative RT. The type of ICIs included were anti- PD-(L)1 and anti-CTLA-4 agents. The primary outcomes assessed were overall survival (OS) and progression- free survival (PFS), along with treatment-related adverse events (TRAEs) grade 3 to 5. Hazard ratios (HRs) were pooled using the generic-inverse variance method under a random-effects model to account for heterogeneity among trials. Binary data was presented using risk ratios, unless a study contained a zero cell for the respective variable, in which case a Peto-Odds ratio was used. Results: 4536 studies were initially identified. After applying inclusion/exclusion criteria, 41 full-text studies were assessed, out of which 9 unique RCTs met our criteria. The included RCTs enrolled patients with a range of metastatic solid tumors, including NSCLC, RCC, melanoma, urothelial carcinoma, HNSCC, adenoid cystic carcinoma, Merkel cell carcinoma, and SCLC. The 9 studies included 493 participants, with 243 participants in the ICI-RT group, and 250 participants in the ICI only group. No statistically significant
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