S740
Clinical – Lower GI
ESTRO 2026
and to downstage the primary tumor, facilitating optimal surgical outcomes. Adaptive radiotherapy (ART) represents a further advancement by leveraging online adaptations to account for interfractional anatomical changes, enabling margin reduction and tighter target delineation. There can be potential implications for toxicity reduction and oncologic outcomes, ART may synergize with neoadjuvant strategies to optimize preoperative treatment, minimizing toxicity through reduced planning target volume margins. Therefore, we decided to review the toxicity outcomes at our center, the Hospital Universitario de Navarra (HUN). Material/Methods: We did a descriptive analysis of toxicity and response in patients with localy advanced rectal adenocarcinoma, during 2023–2025, treated with short-course neoadjuvant adaptive chemoradiotherapy, with radiation régimen of 25Gy in 5 fractions, using theVarian/EthosARTsystem, with CTV-PTV margin of 3 mm, at our center (HUN). Results: We treated 30 patients with a prescribed dose of 25 Gy in 5 fractions between november of 2023 and July of 2025, in combination with XELOX in 28 patients; the remaining 2 patients received FOLFIRI. Of these, 18 were men and 12 women. The mean age was 67 years (range 47–78).At diagnosis, TNM staging comprised: 8 patients with T3N1, 17 with T3N2, and 5 with T4N2. Pathology was located in the upper rectum in 33%, mid-rectum in 17%, and lower rectum in 50% of cases. Complete response (CR) was achieved in 8 patients, of whom 6 were managed with a watch-and- wait approach and 2 underwent definitive intervention. Partial response (PR) was observed in 17 patients and no response in 5; among the PR and no response, 17 underwent further intervention, and the other 5 proceeded to systemic therapy. Regarding toxicity, 14 patients experienced acute toxicity in the form of enteritis, dysuria, and tenesmus, distributed as 4 pacients had G1, 8: G2, 1: G3, and 1 pacient had G4. Three patients progressed despite treatment. The remaining patients are under follow-up.
Conclusion: Using ePROMs to assess quality of life after colorectal cancer treatment is feasible and can provide valuable information to facilitate patient-centred care. Rectal cancer patients, who generally have worse function after treatment, could be targeted with self- management measures through automated pathways as planned with CITRuS2. References: 1. Wheelwright S, Permyakova NV, Calman L, Din A, Fenlon D, et al. (2020) Does quality of life return to pre-treatment levels five years after curative intent surgery for colorectal cancer? Evidence from the ColoREctal Wellbeing (CREW) study. PLOS ONE 15(4): e0231332. https://doi.org/10.1371/journal.pone.02313322. Graupner C, Kimman ML, Mul S, Slok AHM, Claessens D, Kleijnen J, Dirksen CD, Breukink SO. Patient outcomes, patient experiences and process indicators associated with the routine use of patient-reported outcome measures (PROMs) in cancer care: a systematic review. Support Care Cancer. 2021 Feb;29(2):573-593. doi: 10.1007/s00520-020-05695-4. Epub 2020 Sep 2. PMID: 32875373; PMCID: PMC7767901. Keywords: ePROMs, Quality of Life, Organ preservation
Digital Poster 4447
Toxicity after short-course neoadyuvant chemorradiation with online adaptive radiotherapy for rectal cancer Libe Amondarain 1 , Maria Ujue Ruiz 1 , Maribel
Martinez 1 , Patricia Lorenzana 1 , Mario Martin 2 , Sara Lopez 1 , Cristina felipe 1 , Darwin Enrique Pozo 1 , Laura Casaña 1 , Ana Marza 1 , Paula Calvo 1 , Amaya Sola 1 , Marta Barrado 1 , Mikel Rico 1 , Elena Villafranca 1 1 Radiation Oncology, Hospital Univerditario de Navarra (HUN), Pamplona, Spain. 2 Medical Physics, Hospital Univerditario de Navarra (HUN), pamplona, Spain
Purpose/Objective: The management of locally advanced rectal
adenocarcinoma relies on neoadjuvant concurrent chemoradiation to reduce the risk of local recurrence
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