With the rapidly changing landscape of rectal cancer treatment, it is becoming increasingly challenging for clinicians to interpret and synthesise the vast amount of high-quality evidence being generated. A core outcome set (COS) for clinical trials in rectal cancer would help address issues surrounding outcome selection and reporting. The purpose of this research project is to develop a COS to be used in research comparing different treatment paradigms in the management of rectal cancer.

This will be a mixed-methods project, including a systematic review, semi-structured interviews and a Delphi consensus process. The project was designed in accordance with the COMET (Core Outcome Measures in Effectiveness Trials) Handbook, which provides a framework for COS development based on existing evidence. A multidisciplinary Study Advisory Group, composed of rectal cancer providers, methodologists and patients, will oversee the project. A systematic review will be performed to identify an inclusive list of outcomes reported by researchers in previous rectal cancer trials. Outcomes will be collapsed into various core areas and domains according to the OMERACT Filter V.2.0. Semi-structured interviews with rectal cancer survivors and their partners/caregivers will help identify additional patient-centric outcomes not captured in the systematic review. Finally, after a final list of outcomes is generated, patients and healthcare professionals will be invited to participate in a Delphi process to develop the final COS.

The study has received full approval with the Research Ethics Committee at the Integrated Health and Social Services Network for West-Central Montreal (health network responsible for the Jewish General Hospital) (REC: 2025-4377) and the Institutional Review Board of the Mount Sinai School of Medicine (IRB: STUDY-25-00515). The results of this study will be presented at national and international meetings and a manuscript will be submitted for publication in a high-impact surgery and/or oncology peer-reviewed journal.

The study was registered in the COMET database in December 2023 (https://www.comet-initiative.org/Studies/Details/2941). The full systematic review protocol, along with the search strategy and inclusion/exclusion criteria, was registered online in September 2023 (researchregistry.com; reviewregistry1705).