MR-guided focal SBRT uses MRI target localization to deliver high-dose hypofractionated radiation.

This City of Hope Medical Center pilot evaluates focal magnetic resonance–guided stereotactic body radiation therapy (MR-guided SBRT), a device-enabled radiation approach (not a drug) that uses on-table MRI to localize the dominant lesion and confine high-dose radiation to a unilateral treatment region while sparing nearby bladder/rectum. The design is a single-arm feasibility/safety study in NCCN low- or intermediate-risk prostate cancer with unilateral disease (MRI-visible dominant lesion(s) and all biopsy-proven cancer confined to one lobe), with biopsies and MRI follow-up to track both toxicity and local control signals. Patients receive five SBRT fractions over about 2 weeks, plus CT simulation, serial MRI, questionnaires, and surveillance biopsy (including planned sampling inside vs outside the radiation field to study microenvironment and clonal dynamics). The key angle is focal, MR-guided precision as a way to reduce urinary/rectal adverse effects versus broader-field radiotherapy. For many low-risk patients today, care is active surveillance; for intermediate-risk disease, common options include prostatectomy or whole-gland radiation (often hypofractionated/SBRT), with focal approaches still investigational.