A prospective study of 23 patients using daily iterative CBCT and hybrid deformable image registration demonstrates a three-step increasingly refined alignment protocol (bone → prostate → anterior rectal wall) using the 65 Gy isodose line as a reference enables complete elimination of the posterior planning margin (0 mm) without sacrificing coverage of dominant intraprostatic lesion if it is > 0.7 mm from the rectum or overlaps < 1.5 cc with rectum 2 mm-PRV. | Gao, Pract Radiat Oncol 2026
