ESTRO 2025 - Abstract Book

S1801

Clinical – Upper GI

ESTRO 2025

Conclusion: The accumulated dose to OARs was lower than planned with no association between the accumulated dose and toxicity. In terms of local disease progression, higher D min for GTV was associated with a longer time to local disease progression. This has implications for improving patient outcomes by increasing local control and reducing treatment related toxicities. Further research will be carried out to validate these results in a larger cohort.

Keywords: Toxicity, MR-guided, pancreatic SABR

References: 1. Daly M. Vasquez Osorio E. Choudhury A. McWilliam A. Radhakrishna G. Eccles C.L. Evaluation of accumulated OAR dose DIR methods for MR-guided pancreas SABR. Radiother Oncol. 2024;194:S3635-S3636

2501

Mini-Oral Radical hypofractionated radiotherapy with capecitabine for unfit esophageal cancer patients: a phase II study (CRADLE / NL75846.029.20). Leigh A.P. Bruijs 1 , Maarten C.C.M. Hulshof 1 , Paul M. Jeene 2 , Elisabeth D. Geijsen 1,3 , Jolanda Oosterling 4 , Cathrien Tromp 5 , Suzanne S. Gisbertz 6,3 , Mark I. van Berge Henegouwen 6,3 , Rob H.A. Verhoeven 7,4 , Sarah Derks 4,3 , Hanneke W.M. van Laarhoven 4,3 , Peter S.N. van Rossum 1,3 1 Radiation Oncology, Amsterdam UMC, Amsterdam, Netherlands. 2 Radiation Oncology, Radiotherapiegroep, Deventer, Netherlands. 3 Cancer Treatment and Quality of Life, Cancer Center Amsterdam, Amsterdam, Netherlands. 4 Medical Oncolocy, Amsterdam UMC, Amsterdam, Netherlands. 5 Medical Oncolocy, Gelre Ziekenhuis, Apeldoorn, Netherlands. 6 Surgery, Amsterdam UMC, Amsterdam, Netherlands. 7 Research and Development, Netherlands Comprehensive Cancer Organization (IKNL), Utrecht, Netherlands Purpose/Objective: Medically inoperable patients with curable esophageal cancer typically receive definitive chemoradiotherapy (50 50.4 Gy/25-28 fractions and intravenous chemotherapy). This treatment may cause significant toxicity, especially in elderly patients. For those unfit for chemoradiotherapy, Dutch guidelines recommend high-dose palliative hypofractionated radiotherapy of 50 Gy/16 fractions (without chemotherapy), which is generally associated with an acceptable grade ≥3 toxicity rate (10-20%). Unfortunately, this regimen is considered non-curative, with a median overall survival (OS) in real-world data of only 11-13 months. We hypothesized that adding capecitabine (an oral radiosensitizer) may improve disease control. Therefore, we conducted a phase II study to assess the feasibility of a chemoradiotherapy regimen of 50 Gy/16 fractions (during 3.2 weeks) with bidaily capecitabine in patients with inoperable esophageal cancer unfit for standard chemoradiotherapy. Material/Methods: A non-randomized, single-arm phase II study was conducted in 2 centers (June 2021-October 2024). Patients with biopsy-confirmed cT1-4aN1-3M0 esophageal or gastro-esophageal junction cancer, unfit for standard chemoradiotherapy and/or surgery, were treated with hypofractionated radiotherapy (16x3.125 Gy) combined with bidaily capecitabine (2x825 mg/m 2 on radiotherapy days). The primary endpoint was compliance, defined per patient as completing ≥15 of 16 fractions and ≥75% of the total capecitabine dose. Feasibility of the regimen was predefined as finding that ≥70% of patients would meet the compliance criterium. Secondary endpoints included toxicity (CTCAE v4.0), progression-free survival (PFS), and OS. Results: A total of 28 patients were included; 16 (57%) with adenocarcinoma and 12 (43%) with squamous cell carcinoma. Most patients were elderly and in poor physical condition (Figure 1). The compliance criterium was met in 96% of patients (n=27; 95% CI: 82%-100%), which was significantly superior to the predefined acceptable threshold of 70%