MR-guided Single-fraction SBRT for Nodal Oligorecurrent Prostate Cancer (PINPOINT)

PINPOINT is a prospective, investigator-initiated, single-centre, single-arm phase 2 trial of single-fraction MR-guided SBRT in patients with nodal oligorecurrent prostate cancer. Eligible men have PSMA-PET/CT-verified nodal relapse in the pelvis or abdomen following curatively intended local treatment. All patients are simulated with MRI in treatment position and treated with 24 Gy in 1 fraction to the gross tumour volume (GTV) using inverse-planned step-and-shoot IMRT on an MR-linac. No CTV margin is added (CTV = GTV); PTV margins account for motion and set-up uncertainty. Normal-tissue constraints are prioritised over target coverage. The primary endpoint is cumulative CTCAE v5 grade ≥4 treatment-related toxicity within 6 months. Sample size follows a Simon two-stage design (H0: grade 4-5 TRAE rate 15%; H1: 4%; one-sided α = 5%, power 80%), with an interim analysis after 6-month follow-up of the first 16 patients and a total of 48 patients. Follow-up continues for 5 years. Toxicity (CTCAE v5), quality of life (EQ-5D-5L, EORTC QLQ-C30) and patient-reported outcomes (PRO-CTCAE) are collected at baseline and through follow-up; PSA and PSMA-PET/CT (on rising PSA) follow standard of care.