S1074
Clinical – Upper GI
ESTRO 2026
automatic beam gating. Online adaptive radiotherapy (ART) was applied as needed to meet organ-at-risk constraints; no fiducial markers were used. Toxicities were graded per CTCAE v5.0, and tumor response was assessed by RECIST v1.1. Locoregional failure (LRF), distant failure (DF), and overall survival (OS) were estimated using the Kaplan–Meier method. Results: Between 2019-2025, 11 patients (13 tumors) with median age of 68 years (range, 54-82) were evaluated. Most were female (63.6%), had tumors in the pancreatic head (81.8%), and were low- (81.8%) or intermediate-grade (18.2%). Two patients had metastatic disease at presentation. Median tumor size was 3.2 cm (range, 0.8-9.7). All had an ECOG performance status 0-1. Prior to MRgRT, 5 patients had received ≥ 1 systemic therapies; one underwent irreversible electroporation.Median prescribed dose was 50.0 Gy (range, 40.0-78.3) in 5 fractions (range, 5- 30), with median BED10 of 100 Gy10 (range, 72.0- 102.7); 63.6% received BED10 ≥ 100 Gy10. An elective target volume was commonly used (54.5%). ART was used in 7 treatment courses, with 91.4% of fractions adapted. Median GTV, CTV, and PTV volumes were 54.1 cc, 107.0 cc, and 80.1 cc, respectively. Median mean, min, and max doses were 60.3 Gy, 39.0 Gy, and 68.7 Gy for GTV; 57.2 Gy, 35.3 Gy, and 68.3 Gy for CTV; and 57.1 Gy, 38.9 Gy, and 68.7 Gy for PTV. Median D95%, D90%, and D80% were 49.4 Gy, 51.9 Gy, and 56.7 Gy for GTV; 49.8 Gy, 51.3 Gy, and 53.3 Gy for CTV; and 47.5 Gy, 49.8 Gy, and 52.7 Gy for PTV.Median follow-ups from diagnosis and MRgRT were 42.5 and 22.8 months, respectively. Disease control was achieved in 9 patients, with 2 experiencing DFs without LRF. No LRFs or Grade ≥ 2 toxicities were observed. One- and three-year OS from MRgRT were 72.7% and 63.6%, respectively. Conclusion: Dose-escalated MRgRT achieves durable locoregional control and favorable survival for patients with WD- PNETs, with minimal toxicity. Prospective studies are needed to better define the role of MRgRT. Keywords: Neuroendocrine, Pancreas, MR-Guided Radiotherapy
on planning and follow-up CT scans. Descriptive statistics were used for analysis. Results: All 20 patients successfully completed SBRT using two UC for image-based alignment across all five treatment fractions, with translational SE maintained within ≤ 3 mm on verification CBCT (TSR = 100%). The mean translational SE were 0.024 ± 0.052 mm (X), 0.063 ± 0.098 mm (Y), and 0.090 ± 0.109 mm (Z), confirming sub-3 mm accuracy and high reproducibility across all treatment fractions. On follow-up contrast-enhanced CT, no loss or migration of UC markers was detected (MR = 0%). Conclusion: Off-label use of UC as FM demonstrated excellent technical feasibility, positional stability, and safety for image-guided liver SBRT in DIBH-coached patients. Their cost-effectiveness, minimal artefact profile, and compatibility with standard CBCT-based workflows make UC a reliable alternative to conventional metallic FM. Keywords: Hepatocellular carcinoma, fiducial markers, SBRT Neuroendocrine Tumors of the Pancreas with Dose-Escalated Magnetic Resonance-Guided Radiation Therapy Robert A Herrera 1 , Maria Ayala 1 , Adeel Kaiser 1,2 , Kathryn E Mittauer 1,2 , Rupesh Kotecha 1,2 , Matthew D Hall 1,2 , Yongsook C Lee 1,2 , Alonso N Gutierrez 1,2 , Horacio Asbun 3 , Antonio Ucar 4 , Fernando De Zarraga 4 , Santiago Aparo 4 , Minesh P Mehta 1,2 , Michael D Chuong 1,2 1 Radiation Oncology, Miami Cancer Institute, Miami, USA. 2 Herbert Wertheim College of Medicine, Florida International University, Miami, USA. 3 Surgical Oncology, Miami Cancer Institute, Miami, USA. 4 Medical Oncology, Miami Cancer Institute, Miami, USA Digital Poster 1662 Management of Well-Differentiated Purpose/Objective: Well-differentiated pancreatic neuroendocrine tumors (WD-PNETs) are rare and typically managed with surgery and/or systemic therapy. Nonoperative local treatment approaches remain understudied, and the role of radiotherapy in such tumors is evolving. Magnetic resonance (MR)–guided radiotherapy (MRgRT) enables safe dose escalation while sparing surrounding healthy tissues, potentially improving local control and long-term outcomes. Material/Methods: We retrospectively analyzed WD-PNETs treated with MRgRT in mid-inspiration breath-hold on a 0.35-T MR- linac using continuous intrafraction tracking with
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The Safety and efficacy of the addition of multi-site multimodal radiotherapy into Subsequent-line treatment for advanced liver cancer a-Qin Zhao 1 , Guixia Wei 2 , Guang-Jun Li Li 2 , Xiao-Wei Zhao 2 , Ye chen 2 , Qing Fang Li 2 , Xian Zhou Huang 2 , Yuan Feng Wei 2 , Rong Tang 2 1 cancer, west china hospital, sichuan, China. 2 cancer center, west china hospital, sichuan, China
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