ESTRO 2025 - Abstract Book

S1178

Clinical – Lower GI

ESTRO 2025

1624

Poster Discussion Patient experience assessment with serial sampling for research in rectal cancer radiotherapy trials: use of the Decision Regret Scale. Ross K McMahon 1 , Sean M O'Cathail 2 , Catherine Hanna 3 , Janet Graham 2 , Mark Saunders 4 , Nicholas MacLeod 2 , Rebecca Muirhead 5 , Leslie Samuel 6 , Richard Adams 7 , Lynsey Devlin 2 , Lucy Wells 6 , Claire Arthur 4 , Caroline Kelly 8 , Liz anne Lewsley 8 , Lucy Paterson 8 , Nicola Walker 8 , Lily Hillson 9 , Ashley K McCulloch 9 , Chia Y Kong 1 , Campbell SD Roxburgh 1 1 Academic Unit of Surgery, School of Cancer Sciences, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom. 2 Beatson West of Scotland Cancer Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, United Kingdom. 3 School of Cancer Sciences, University of Glasgow, Glasgow, United Kingdom. 4 The Christie, NHS Foundation Trust, Manchester, United Kingdom. 5 Oxford University Hospital, NHS Foundation Trust, Oxford, United Kingdom. 6 Department of Oncology, Aberdeen Royal Infirmary, NHS Grampian, Aberdeen, United Kingdom. 7 Centre for Trials Research Cardiff University Heath Park, Cardiff University and Velindre NHS Trust, Cardiff, United Kingdom. 8 Glasgow Oncology Clinical Trials Unit, School of Cancer Sciences,, University of Glasgow, Glasgow, United Kingdom. 9 Wolfson Wohl Cancer Research Centre, School of Cancer Sciences, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom Purpose/Objective: In an era of novel radiotherapy (RT) strategies, embedding translational research into trials to understand novel drug-RT target tissue interaction is essential. In rectal cancer, access to tissue is available via proctoscopy, which is considered an invasive test. The study of patient tolerability and acceptability is required if proctoscopy is to be used more frequently for research or monitoring tumour response. We aimed to report patient experience and perceptions of serial proctoscopy in locally advanced rectal cancer(LARC). The Decision-Regret-Scale (DRS) is a validated means of assessing patient distress or remorse after a heath care decision. 1 Material/Methods: Two prospective serial tissue sampling projects of LARC patients undergoing RT were utilised. Study A ( IRAS-ID 239609) sampled standard-of-care, and Study B (NCT04621370) 2 was a clinical trial of an investigative medicinal product(CTIMP) . Patients voluntarily attended 4 additional proctoscopy biopsies at a time-point prior to, and at 2-, 6- , and 12 or 16-weeks after commencing long-course (45–54Gy/25#) or short-course (25Gy/5#) RT. Following completion, patients were given the option to complete a DRS and provide free-text feedback regarding their decision to participate. Results: Between November 2020 and April 2024, a combined total of 45 DRSs were completed (29 Study A, 16 Study B). Relating to participation in the study, patients; Strongly Agreed (91%) or Agreed (9%) “It was the right decision”, Strongly Disagreed (84%) or Disagreed (13%) that they “regret the choice that was made”, Strongly Agreed (84%) or Agreed (16%) they “would go for the same choice if I had to do it over again”, Strongly Disagreed (82%) or Disagreed (16%) that “the choice did me a lot of harm”, and Strongly Agreed (87%) or Agreed (13%) that “the decision was a wise one”. On thematic analysis of Study A free-text, 24% reported participation relieved anxieties relating to cancer and treatment, 28% benefitted from witnessing serial changes to their tumour, 21% felt more informed, and 21% benefited from helping contribute to research. Conclusion: This is the first report of patient reported experience with serial sampling protocols in the context of rectal cancer RT trials. Patients overall provided favourable responses when considering their decision making around participation. We report additional perceived patient benefits, and importantly, that tests appear well tolerated. Collection of patient reported experience measures, such as the DRS, is essential to build evidence for tolerability and acceptability of research assessments, and inform on novel clinical trial design incorporating translational research sampling protocols.