Prospective phase II study of stereotactic body proton therapy for treatment of primary renal cell carcinoma (SPARE): clinical trial protocol. - Shaaban, Sherif G; Chen, Hao; Singla, Nirmish; Tran, Anh; Hu, Chen; Ke, Suqi; Jarrett, Thomas W; Deville, Curtiland (BMC Cancer, 2025)