This is an interventional, single-centre, single-arm, non-randomized, prospective, feasibility trial investigating salvage MR-guided High-Dose-Rate brachytherapy for prostate bed recurrence after postoperative radiotherapy.

Patients who received previous adjuvant or salvage radiotherapy to the prostate bed >

Isolated prostate bed recurrence based on PSMA PET, biopsy-proven, and MR visible >

Baseline: QoLs questionnaires, PSA, pelvic magnetic resonance imaging (MRI) scan for RT planning >

Two fractions of 13 Gy each delivered over 7-21 days. GTV(HDR) delineation (based on MRI-guided and PSMA PET, biopsy data as applicable) >

Follow-Up after treatment 60 months: PSA, CTCAE v5.0, MRI pelvis +/- PSMA-PET scan (optional at 24 months)

Inclusion Criteria:

1. Patients who received previous RT to the prostate bed +/- pelvic nodal regions
2. Prostate-bed recurrence identified by biopsy and/or MRI and/or PSMA-PET scan
3. At least two continuous PSA elevations post RT and PSA above 0.2 ng/dl
4. With or without ADT PSA doubling time from nadir greater than 6 months
5. ECOG 0-2
6. Age greater than 18 years

Exclusion Criteria:

1. Radiological (e.g. PSMA PET, CT, MRI or bone scan) evidence of or distant metastases
2. History of ≥G3 gastrointestinal (GI) and genitourinary (GU) toxicities following RT
3. Any contraindications to MR and/or brachytherapy