Outcome reporting in studies on sacrococcygeal teratoma (SCT) is highly heterogeneous, which limits comparability across studies and thus hampers the development of international treatment guidelines.

Variation in treatment and access to facilities contributes to differences in outcome reporting between centres and countries. Establishing a Core Outcome Set (COS) can improve consistency in outcome reporting and facilitate global collaboration and data comparison. We therefore aim to develop a Core Outcome Set for SCT (COS-SCT) using the Delphi method to achieve consensus on key outcomes. This will enhance the standardisation of outcome reporting and improve the quality of research and clinical care for SCT patients globally.

The development of the COS-SCT will consist of three phases. First, a systematic review will be performed to identify outcomes reported in studies on the surgical treatment of SCT in children. Second, an international Delphi survey will be conducted among key stakeholders, including clinicians, researchers and patient representatives, to establish consensus on outcome prioritisation. Finally, a consensus meeting with representatives from all stakeholder groups will be held to ratify the final Core Outcome Set. The study will follow methodological guidance from the Core Outcome Measures in Effectiveness Trials (COMET) initiative and will be developed and reported in accordance with the Core Outcome Set Standards for Development (COS-STAD) and Core Outcome Set Standards for Reporting (COS-STAR).

The medical research ethics committee of the Amsterdam University Medical Centre (Amsterdam UMC) confirmed that the Dutch Medical Research Involving Human Subjects Act (WMO) does not apply to this study, and therefore a full review by the ethics committee is not required. This study is registered in the COMET initiative database. Results will be disseminated in peer-reviewed academic journals and conference presentations.

Trial registration number: COMET registration number 3485