ESTRO 2025 - Abstract Book

S672

Clinical - CNS

ESTRO 2025

1457

Digital Poster Outcomes of whole-brain radiotherapy with stereotactic boost using HyperArc mono-isocentric radiosurgery: a single-institution study of 105 patients. Camille STREIFF 1 , Nicolas DEMOGEOT 1 , Vincent MARCHESI 1 , Jean-Michel TRINH 2 , Aboubacar DIALLO 3 , William GEHIN 1 1 Radiotherapy, ICL, NANCY, France. 2 Radiology, ICL, Nancy, France. 3 Biostatisticss, ICL, Nancy, France Purpose/Objective: The treatment of multiple brain metastases presents significant challenges, particularly in patients ineligible for strict stereotactic radiosurgery (SRS). The addition of a stereotactic simultaneous integrated boost (sSIB) enhances local control of visible metastases while preserving the global whole-brain radiotherapy (WBRT) approach to prevent distant metastases. HyperArc enables the delivery of focused doses with optimized gradients, while reducing exposure to healthy brain tissues.This study aims to evaluate the efficacy of sSIB in addition to WBRT using the Hyperarc technique. Material/Methods: We conducted a retrospective, monocentric analysis of 105 patients treated with WBRT combined with a sSIB between October 2019 and October 2023. WBRT was delivered at 30 Gy over 10 fractions, with a SIB of 40 Gy targeting 1–10 brain metastases (≥5 mm). All treatments were administered using the HyperArc Volumetric Modulated Arc Therapy (HA-VMAT) technique on a TrueBeam accelerator (Varian®). The primary endpoint was to evaluate intracranial progression-free survival (iPFS), and the secondary endpoints included overall survival (OS), treatment-related toxicity, and identification of predictive factors. Results: The median age was 63 years (IQR, 56–69 years), and 74% of the patients had extracranial metastases. Lung (68%) and breast (14%) tumors were the most frequent. The median number of brain metastases was 6 (IQR: 4–10), with a median total boosted volume of 14 cm³ (IQR: 7–24). The median follow-up period was 12 months (range: 0–46 months). The median iPFS period was 6.3 months (95% CI: 3.75–7.62), with 6-months, 9-months, 12-months and 24-months iPFS rate respectively of 51,6%, 33,3%, 24,7% and 7,5%. Twenty-seven patients (25,7%) experienced cerebral recurrence (local or distant), and only eleven (10,5%) experienced recurrence of boosted lesions. The median OS period was 8.7 months (95% CI: 6.96–12.2), with 6-months, 9-months, 12-months and 24 months OS rate respectively of 60%, 49,5%, 40% and 21,3%. Radionecrosis occurred in 5.7% of the patients. Univariate analysis identified extracranial metastases (hazard ratio [HR]: 2.05, p=0.007) as a significant predictor of progression, whereas combination therapy with immunotherapy or targeted therapies improved iPFS (HR: 0.50, p=0.033). No grade III or IV radiation-induced toxicities were observed. Conclusion: These results show the potential of whole-brain radiotherapy with stereotactic boost as an effective treatment strategy with manageable toxicity for patients with multiple brain metastases.

Keywords: Brain metastases, WBRT plus stereotactic SIB