SMILE-stereotactic multiple fraction radiotherapy for non-spine bone metastases: study protocol for a multicenter, open-label phase III randomized controlled trial.

Background: The SMILE study addresses a significant need in palliative oncology by evaluating the non-inferiority of a shortened, 3-fraction stereotactic body radiotherapy (SBRT) schedule against the traditional 5-fraction approach for non-spine bone metastases in terms of pain control. Optimizing SBRT could significantly enhance the quality of life for patients by providing effective pain relief while minimizing treatment sessions.

Methods: This international, multicenter phase III trial will randomize 162 patients to receive either a 3-fraction regimen (9 Gy per fraction) or a standard 5-fraction regimen (7 Gy per fraction). Outcomes, assessed at 3 months post-treatment, will focus on pain response, quality of life, and control of metastasis. With a hypothesis-driven design, the study will incorporate intent-to-treat and per-protocol analyses, incorporating appropriate measures for data integrity and handling of missing information.

Discussion: If the 3-fraction SBRT regimen demonstrates non-inferiority, it could streamline palliative care protocols, reduce patient burden, and set a new standard for treatment, reflecting a patient-centered approach in palliative radiation oncology.

Trial registration: The trial has been registered prospectively on ClinicalTrials.gov under the identifier NCT05406063, as of May 3, 2022.