Prostate bed and organ-at-risk deformation: Prospective volumetric and dosimetric data from a phase II trial of stereotactic body radiotherapy after radical prostatectomy

•Stabilizing organ-at-risk anatomy (OAR) is essential.•Interfraction prostate bed volume is stable despite deformable surrounding organs.•Target underdosing and OAR overdosing is avoided in post-prostatectomy radiotherapy.•Volumetric and dosimetric changes from rotation and intrafraction motion are minor.•Shape of prostate bed may also influence target coverage.