ESTRO 2025 - Abstract Book

S1253

Clinical – Lower GI

ESTRO 2025

Conclusion: Combination treatment of upfront radiotherapy, immunochemotherapy demonstrated a promising efficacy and a manageable safety profile in MSS LARC with resectable metastases. Translational study to identify predictive biomarkers is ongoing. Clinical trial information: NCT05359393.

Keywords: rectal cancer, MSS, immunotherapy

3809

Digital Poster Cure vs. toxicity: quantifying preferences for non-surgical management of rectal cancer using a prospective discrete choice experiment study Edward JD Webb 1 , Maureen Twiddy 2 , Samantha Noutch 3 , Ravi Adapala 4 , Simon P Bach 5 , Sarah Brown 3 , Carole Burnett 6 , Alwyn Burrage 7 , Alexandra Gilbert 8 , Maria Hawkins 9 , Debra Howard 10 , Eleanor Hudson 3 , Monica Jefford 11 , Rohit Kochhar 12 , Mark Saunders 13 , Jenny Seligmann 8 , Alexandra Smith 3 , Mark Teo 6 , Nicholas West 8 , David Sebag Montefiore 8 , Simon Gollins 14 , Ane L Appelt 8 1 Academic Unit of Health Economics, University of Leeds, Leeds, United Kingdom. 2 Hull York Medical School, University of Hull, Hull, United Kingdom. 3 Leeds Institute of Clinical Trials Research, University of Leeds, Leeds, United Kingdom. 4 Department of Radiology, Wrexham Maelor Hospital, Wrexham, United Kingdom. 5 Academic Department of Surgery, Queen Elizabeth Hospital Birmingham, Birmingham, United Kingdom. 6 Leeds Cancer Centre, University of Leeds, Leeds, United Kingdom. 7 Patient Advocate, Patient Advocate, Conwy, United Kingdom. 8 Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom. 9 Medical Physics and Biomedical Engineering, University College London, London, United Kingdom. 10 National Radiotherapy Trials QA (RTTQA) Group, Mount Vernon Cancer Centre, Northwood, United Kingdom. 11 Patient Advocate, Patient Advocate, London, United Kingdom. 12 Department of Radiology, The Christie NHS Foundation Trust, Manchester, United Kingdom. 13 Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom. 14 Department of Oncology, Shrewsbury and Telford NHS Trust, Shrewsbury, United Kingdom Purpose/Objective: Dose-escalation may increase the chance of successful non-surgical rectal cancer management, but requires an understanding of acceptable trade-offs between chance of cure and toxicity risks. This study is the first to measure patient preferences for non-surgical management (NOM) of rectal cancer using a discrete choice experiment (DCE). Material/Methods: A prospective, multicentre study conducted in seven UK radiotherapy centres. Patients consented to participation prior to initiation of radiotherapy-based NOM for rectal cancer (any stage), and completed the survey pre-treatment and 6 months post-treatment. The DCE was developed with qualitative patient input and had a Bayesian D-efficient design. Patients made repeated choices between hypothetical NOM treatments, described using six attributes: treatment length; chance of being cancer-free two years post-treatment; side effect risks during and two years post treatment; support available. Participants indicated preferences for non-surgical vs. surgical treatment on a Likert scale. Baseline responses were analysed using mixed logit, quantifying trade-offs between attributes, using preference for chance of cure as the unit of measurement. Post-estimation, individual preferences conditional on choices were estimated. Changes in mean preferences pre/post-treatment were analysed using multinomial logit, with the delta method used to test for pre/post-treatment differences. Differences in preferences for surgical/non surgical management were assessed using Mann-Whitney U tests.