S867
Clinical - Mixed sites & palliation
ESTRO 2026
Mairani 2 , Klaus Herfarth 1,2 , Semi B. Harrabi 1,2 , Sebastian Adeberg 3 , Jürgen Debus 1,2 1 Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany. 2 Heidelberg Ion Beam Therapy Center (HIT), Heidelberg University Hospital, Heidelberg, Germany. 3 Radiation Oncology and Particle Therapy Center (MIT), Gießen and Marburg University Hospital, Marburg, Germany Purpose/Objective: Carbon ions have biophysical advantages over photons, including a finite range, increased relative biological effectiveness, and lowered oxygen dependence. Maximum treatment flexibility is attainable with rotational beam delivery. We report our clinical experience using the carbon-ion gantry at the Heidelberg Ion Beam Therapy Center with intensity-controlled raster scanning capability, focusing on treatment toxicity. Material/Methods: A total of 947 patients treated only with carbon ions between 2012 and 2020 were evaluated. Data were analyzed using descriptive statistics. Toxicity analysis was conducted using Common Terminology Criteria of Adverse Events v5.0. Results: The median age preradiotherapy was 55 years (range 18-91). Most patients had locally advanced tumors (49.2% T4; 20.4% T3) without regional lymph node metastases (67.1% N0). The most common treatment indications were sacrococcygeal tumors (n = 204; 21.5%), followed by tumors of the paranasal sinuses (n = 123; 13.0%) and skull base (n = 98; 10.3%). A total of 259 patients (27.3%) received carbon-ion reirradiation, the most frequent carbon-ion gantry treatment indication viewed across all patients. The yearly number of reradiotherapy patients has increased continuously since 2012. The most common particle therapy beam number was 2 (range 1-6). The use of more than 2 beams was particularly frequent in tumors of the skull base (38.8%) and head and neck region (30.3%). High-grade (III-IV) acute and late toxicity rates were 1.3% and 2.4% in primary treatment. Mean numbers of acute and late grade I–II toxicity events per patient were 1.8 (95% confidence interval [CI] 1.4-2.2) and 1.5 (95% CI 1.0-2.0). Conclusion: Carbon-ion RT using a heavy-ion gantry resulted in favorable toxicity rates in specific indications. Further interdisciplinary research demonstrating the clinical benefit of carbon-ion RT is required. This study provides more evidence supporting particle therapy facilities and may serve as a foundation for prospective clinical trials. Keywords: Particle therapy, heavy ions, gantry
reported clinical outcomes. Results:
Patients received 6MV-FFF (n=9), 10MV-FFF (n=34), or 18MV (n=1). Average D50% (ranging from 7 to 10 Gy) increases with energy. Peak doses decrease with increasing depths but remain independent of energy, technique, and anatomic targets. Valley doses (ranging from 2 to 7Gy) have no particular correlation with depth, but are dependent on energy and technique. D10%/D90% (ranging from 3 to 5) and PVDR (ranging from 2 to 8) decreased with energy and depth. Peak widths and p-p distances increased modestly with energy and depth. Higher D5% (>76%), D10% (>68%), and D20% (>59%) were associated with improved PFS. Shorter p-p distances (<1.35 cm at 90% Dmax and <1.31 cm at 50% Dmax) correlated with longer PFS and OS respectively. Tumor site and volume remained independent prognostic predictors: pelvic location and larger-volume tumors are associated with poorer outcomes. IMRT has higher D50%, P/V ratio, peak width and p-p distance compared to GRID block; IMRT also has lower valley doses compared to GRID block.
Conclusion: Dose heterogeneity parameters—D5%, D10%, D20%, and p-p distance—appear to carry predictive significance. These dose threshold findings may inform treatment planning strategies and guide the design of prospective trials to validate their clinical relevance. Keywords: GRID, spatially fractionated radiation therapy
Mini-Oral 1121
Intensity-Controlled Raster Scanning Carbon Ion Radiotherapy with a Heavy-ion Gantry: Clinical Experience at Heidelberg Ion Beam Therapy Center (HIT) Thomas Held 1,2 , Katharina Dvornikovich 1 , Henrik Franke 1 , Malte Ellerbrock 1,2 , Thomas Haberer 2 , Andrea
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