International consensus on palliative radiotherapy endpoints for future clinical trials in bone metastases: A second...

External beam radiotherapy (EBRT) is a well-established and effective intervention for pain palliation in patients with bone metastases. Variability in trial endpoints, however, has limited comparability and synthesis of available evidence. To address this, the International Bone Metastases Consensus Working Party published endpoint guidelines in 2002 and updated them in 2012. This study aims to review, re-evaluate, and update the existing consensus to reflect contemporary clinical practice and technological advances.

A modified Delphi process was undertaken, informed by a systematic literature review and post-2012 guideline publications. An electronic survey was distributed to previous contributors and internationally recognized bone EBRT experts. In Phase I, statements achieving ≥ 75 % agreement were accepted. Items not reaching consensus were refined by the Working Party, discussed by a core panel of eight experts, and recirculated in Phase II. Descriptive statistics summarized response rates and agreement levels.

Of 125 experts invited, 58 participated in Phase I, and 44 in Phase II. Consensus was achieved for 38 out of 49 statements (78%), including 18 new or revised items. Key recommendations addressed eligibility criteria for trial enrolment, standardized pain and analgesic assessments, specification of radiation techniques and dose schedules, follow-up intervals, assessment timing and modalities, and incorporation of cost-effectiveness analyses.

This updated consensus provides a contemporary, standardized framework for EBRT trial design and reporting in bone metastases. Adoption will improve cross-study comparability and guide future research priorities. Regular updates are planned to ensure alignment with evolving clinical practice and technology.