ESTRO 2025 - Abstract Book

S1755

Clinical – Upper GI

ESTRO 2025

2. Zaafouri H, et al. Comparison between signet-ring cell carcinoma and non-signet-ring cell carcinoma of the stomach: clinicopathological parameters, epidemiological data, outcome, and prognosis-a cohort study of 123 patients from a non-endemic country. World J Surg Oncol. 2022 Jul 20;20(1):238. 3. Park SH, et al; ARTIST 2 investigators. A randomized phase III trial comparing adjuvant single-agent S1, S-1 with oxaliplatin, and postoperative chemoradiation with S-1 and oxaliplatin in patients with node-positive gastric cancer after D2 resection: the ARTIST 2 trial. Ann Oncol. 2021 Mar;32(3):368-374.

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Digital Poster Long-term outcomes of MR-guided stereotactic body radiation therapy for pancreatic oligometastases from renal cell carcinoma Jonna K. van Vulpen 1 , Hidde Eijkelenkamp 1 , Guus Grimbergen 1 , Frank J. Wessels 2 , Sasja F. Mulder 3 , Gert J. Meijer 1 , Martijn P.W. Intven 1 1 Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 2 Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands. 3 Department of Radiation Oncology, Radboudumc, Nijmegen, Netherlands Purpose/Objective: Patients with pancreatic metastases from renal cell carcinoma (RCC) often have a favorable prognosis, with standard treatment typically being surgery or systemic therapy. Stereotactic body radiation therapy (SBRT) may be a non-invasive alternative strategy if it can achieve acceptable toxicity and high local control rates. However, conventional CT-based SBRT may be challenging because of limited visibility, day-to-day anatomic variation, and patients often presenting with multiple metastases. These issues may be overcome by MR-guided delivery. Therefore, this study evaluated MR-guided SBRT for pancreatic oligometastases from RCC, focusing on long-term oncological outcomes and technical feasibility. Material/Methods: We reviewed all patients treated with MR-guided SBRT for pancreatic oligometastases from RCC at a single institute. We assessed adverse events (AE), freedom from local progression (FFLP), progression-free survival (PFS), and freedom from start of systemic therapy (FFST). Technical feasibility was assessed using dose-volume histogram (DVH) parameters of the target (GTV V100% and PTV V95%) and critical organ at risk (OAR) constraints (duodenum, bowel, and stomach D0.5cc). Results: From June 2019 to September 2022, 11 patients with a total of to 31 pancreatic oligometastases from RCC were treated with MR-guided SBRT. Patients had a mean age of 65.6 years (±6.8) and a median of 3 irradiated pancreatic metastases (range 1-7). Treatment regimens were 5 fractions of 7 Gy (n=1 metastasis) or 8 Gy (n=30 metastases) per fraction. Figure 1 provides imaging and a sample online treatment plan for a patient with three lesions. At a median follow-up of 31.6 months (IQR 26.0 – 37.8 months), one grade 3 adverse event (bleeding) was observed. FFLP was 100% at 1 year and 95% at 2 years. PFS was 81% at 1 year, and 94% at 2 years. FFST was 91% at 1 year and 82% at 2 years. Kaplain-Meier curves for FFLP, PFS and FFST are shown in Fig. 2. Over all fractions and lesions, the median GTV V100% and median PTV V95% were 96.1% and 93.3% respectively, with OAR D0.5cc remained well under constraints.