S888
Clinical - Mixed sites & palliation
ESTRO 2026
Takayuki Sakurai 1,2 , Masashi Taka 3 , Mizuho Ishiyama 4 , Hiroyuki Hondo 5 , Shigeyuki Takamatsu 1 , Satoshi Kobayashi 6 , Eiichi Mizuno 2 1 Radiation Oncology, Kanazawa University Hospital, Kanazawa, Japan. 2 Radiation Oncology, Toyama CyberKnife Center, Toyama, Japan. 3 Radiation Oncology, Toyama Prefectural Central Hospital, Toyama, Japan. 4 Radiation Oncology, Koseiren Takaoka Hospital, Takaoka, Japan. 5 Neurosurgery, Gofuku Neurosurgical Clinic, Toyama, Japan. 6 Radiology, Kanazawa University Hospital, Kanazawa, Japan Purpose/Objective: Large brain metastases frequently cause neurological symptoms and pose therapeutic challenges [1]. This retrospective study evaluated whether initial tumor response after SRT correlates with neurological symptom improvement and overall survival (OS) in patients with large symptomatic brain metastases. Material/Methods: We retrospectively analyzed 83 patients (92 lesions) with large brain metastases (diameter > 3 cm or PTV ≥ 10 cc) and baseline symptoms, treated with CyberKnife SRT between 2012 and 2024, with available post- treatment imaging. SRT was most commonly delivered as 35 Gy in 5 fractions (to D95 of the PTV). The median age was 71 years, and 53% had a KPS ≥ 70. Primary tumors included lung (n = 45), breast (n = 12), and others (n = 26). Initial tumor response and neurological symptoms were evaluated concurrently 1–3 months post-SRT. Tumor response was assessed according to the Response Assessment in Neuro- Oncology Brain Metastases criteria [2], and symptoms were classified as resolved, improved, unchanged, or worsened. Associations between tumor response and symptom improvement were analyzed using Fisher’s exact test. Prognostic factors for OS were assessed via Cox regression. Results: Median follow-up was 26.2 months (95% CI: 15.6– 52.2). Treated lesions had a median maximum diameter of 33.9 mm (range 25.7–53.3) and a median PTV of 14.9 cc (range 10.0–39.2). The initial tumor response assessment was performed at a median of 2.2 months (IQR: 1.3–2.6 months) after SRT. At initial tumor response, 16 patients achieved a CR, 56 had a PR, 9 had SD, and 2 had PD, resulting in an objective response rate (CR/PR) of 86.8%. Neurological symptoms improved or resolved in 67 patients (80.7%) (resolved in 29, improved in 38). Tumor shrinkage (CR/PR) was significantly associated with symptom improvement (p = 0.001, Fisher’s exact test; Table 1). On multivariate analysis, KPS ≤ 60 (HR 2.12, p = 0.021), non-CR at initial tumor response (HR 6.75, p = 0.004), and uncontrolled extracranial disease (HR 6.61, p <
References: [1] Brown PD, Jaeckle K, Ballman KV, et al. Effect of Radiosurgery Alone vs Radiosurgery With Whole Brain Radiation Therapy on Cognitive Function in Patients With 1 to 3 Brain Metastases: A Randomized Clinical Trial. JAMA. 2016;316:401-9. https://doi.org/10.1001/jama.2016.9839.[2] Makale MT, McDonald CR, Hattangadi-Gluth JA, et al. Mechanisms of radiotherapy-associated cognitive disability in patients with brain tumours. Nat Rev Neurol. 2017;13:52-64. https://doi.org/10.1038/nrneurol.2016.185.[3] Okoukoni C, McTyre ER, Ayala Peacock DN, et al. Hippocampal dose volume histogram predicts Hopkins Verbal Learning Test scores after brain irradiation. Adv Radiat Oncol. 2017;2:624-9. https://doi.org/10.1016/j.adro.2017.08.013. Keywords: Metastases, Hippocampus, Stereotactic Radiosurgery Digital Poster 2925 Association of initial response after stereotactic radiotherapy for symptomatic large brain metastases with neurological improvement and survival
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