Abscopal responses following stereotactic ablative radiotherapy during immune checkpoint inhibitor therapy in metastatic renal cell carcinoma: protocol for the prospective multicentre observational AURICRE study in Japan.

introductionPatients with metastatic renal cell carcinoma (mRCC) treated with immune checkpoint inhibitors (ICIs) may experience immune-confirmed stable disease (iSD) or progressive disease (iCPD). Abscopal responses following ultra-hypofractionated radiotherapy during immunotherapy have been reported, but their incidence, timing and associated clinical or biological factors remain poorly defined in prospective observational settings. METHODS AND ANALYSIS: AURICRE is a prospective, multicentre observational study that plans to enrol 145 patients with mRCC who exhibit iSD or iCPD during ongoing ICI therapy. Participants undergo stereotactic ablative radiotherapy (SABR) to either the primary tumour or selected metastatic lesions. Prespecified SABR regimens include 42 Gy in three fractions or 40 Gy in five fractions for primary tumours, and fractionated schedules delivering ≥5 Gy per fraction for metastatic sites, with metastatic site regimens corresponding to a BED ETHICS AND DISSEMINATION: This study was approved by the Institutional Review Board of the University of Yamanashi (Approval Number: CS0075). Written informed consent will be obtained from all participants before provisional registration. Study findings will be disseminated through peer-reviewed publications and scientific meetings. TRIAL REGISTRATION NUMBER: This trial is registered at ClinicalTrials.gov (NCT07240610) and the University Hospital Medical Information Network (UMIN000059652); Pre-results.