S951
Clinical - Non-malignant & functional radiotherapy
ESTRO 2026
Embolization followed by hfSRS was performed in 33 patients (32.7%). The median nidus volume was 5.9 cc (0.08–47.8 cc) and 33 patients (32.7%) had a volume ≥ 10 cc. The median prescribed dose was 30 Gy (11–36 Gy) delivered in a median of 5 fractions (1–6). The median EQD23 was 90 Gy (51.3–183 Gy). At a median follow-up of 45 months (3–210 months), partial or complete obliteration was achieved in 86 patients (85.1%), with complete obliteration in 39 patients (38.6%) (Figure 1). The median times to partial and complete obliteration were 6 months (1–74 months) and 24 months (3–76 months), respectively. Pre-hfSRS embolization was not associated with partial or total obliteration (p = 0.9 and p = 0.3, respectively), whereas a nidus volume ≥ 10 cc was associated with a lower likelihood of total obliteration (p = 0.03) but did not affect overall obliteration rate (p = 0.4). Long-term toxicity occurred in 22 patients (21.7%): grade 1 in 8 (7.9%), grade 2 in 12 (11.8%), and grade 3 in 2 (1.9%). Toxicity did not increase with increasing nidus size ( ≥ 10 cc)(p=0.1). During follow-up, one patient experienced bleeding during the latency period prior to obliteration; embolization was performed in one patient and microsurgery in two.
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Hypofractionated Stereotactic Radiosurgery for Arteriovenous Malformations: Expanding the Boundaries of Radiosurgery Melek Tugce Yilmaz 1 , Alper Kahvecioglu 1 , Fatma Ilay Korkmaz Cimen 1 , Anil Arat 2 , Sinan Balci 2 , Mustafa Cengiz 1 , Gozde Yazici 1 1 Radiation Oncology Department, Hacettepe University, Ankara, Turkey. 2 Interventional Radiology Department, Hacettepe University, Ankara, Turkey Purpose/Objective: Arteriovenous malformations (AVMs) are rare congenital vascular anomalies that can be managed with microsurgery, embolization, stereotactic radiosurgery (SRS), or a combination of these modalities. The literature predominantly reports outcomes of single-fraction schedule; however, this approach may not be feasible for large lesions [1, 2]. Herein, we present the occlusion and toxicity outcomes of our hypofractionated SRS (hfSRS) cohort for AVMs. Material/Methods: We retrospectively evaluated 101 patients who underwent hfSRS between July 2007 and October 2023. Patients with a minimum follow-up of two years were included in the analysis. The AVM nidus was delineated as the target volume, and all patients were followed in collaboration with the interventional radiology unit. Treatment-related toxicity was graded according to CTCAE version 5.0. Statistical analyses were performed using SPSS software, version 23.0 (IBM Corp., Armonk, NY, USA). Results: The median age was 28 years (6–70 years). Patient and treatment characteristics are summarized in Table 1.
Conclusion: HfSRS is an effective and well-tolerated treatment option for AVMs, achieving high obliteration rates with low toxicity. Importantly, even in large-volume AVMs ( ≥ 10 cc), hfSRS provided effective lesion control with acceptable safety, extending radiosurgical indications beyond traditionally eligible cases. References: [1] Mohr L, Lishewski P, Schymalla M, Tas KT, Smalec E, Engenhart-Cabillic R, et al. Stereotactic radiosurgery
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