PSMA-PET/MRI-Based Focal Dose Escalation in Patients with Primary Prostate Cancer Treated with Stereotactic Body Radiation Therapy (HypoFocal-SBRT): Study Protocol of a Randomized, Multicentric Phase III Trial.

Technical advances in radiotherapy (RT) treatment planning and delivery have substantially changed RT concepts for primary prostate cancer (PCa) by (i) enabling a reduction of treatment time, and by (ii) enabling safe delivery of high RT doses. Several studies proposed a dose-response relationship for patients with primary PCa and especially in patients with high-risk features, as dose escalation leads to improved tumor control. In parallel to the improvements in RT techniques, diagnostic imaging techniques like multiparametric magnetic resonance imaging (mpMRI) and positron-emission tomography targeting prostate-specific-membrane antigen (PSMA-PET) evolved and enable an accurate depiction of the intraprostatic tumor mass for the first time. The HypoFocal-SBRT study combines ultra-hypofractionated RT/stereotactic body RT, with focal RT dose escalation on intraprostatic tumor sides by applying state of the art diagnostic imaging and most modern RT concepts. This novel strategy will be compared with moderate hypofractionated RT (MHRT), one option for the curative primary treatment of PCa, which has been proven by several prospective trials and is recommended and carried out worldwide. We suspect an increase in relapse-free survival (RFS), and we will assess quality of life in order to detect potential changes.