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

BackgroundThe 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.MethodsThis 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.DiscussionIf 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 registrationThe trial has been registered prospectively on ClinicalTrials.gov under the identifier NCT05406063, as of May 3, 2022.