Study on Prostate Salvage Using High-dose-rate Brachytherapy

The objectives of this prospective, multicenter study are: * Primary: 1\. Biochemical relapse-free survival, defined as the time to biochemical relapse (nadir plus 2 ng/mL - Phoenix criteria). * Secondary: 1. Local relapse-free survival, defined as the time from treatment to local relapse confirmed by imaging (choline PET/MRI). 2. Analysis of acute and chronic toxicity (Common Terminology Criteria for Adverse Events \[CTCAE\] version 5). 3. Assessment of patient quality of life before and after treatment to analyze the impact of local re-irradiation on daily life using the following questionnaires: International Prostate Symptom Score (IPSS), Functional Assessment of Cancer Therapy-Prostate (FACT-P), and European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire - Prostate Module (EORTC QLQ-PR25). Primary outcome measure: Biochemical relapse-free survival, and analysis of toxicity and quality of life in patients treated with salvage brachytherapy following radical treatment. Study population, total number of subjects, and duration: Patients who received radical-intent radiotherapy as their initial treatment (brachytherapy alone, external beam radiotherapy, or external beam radiotherapy plus a brachytherapy boost) and were diagnosed with local recurrence via next-generation imaging techniques (choline PET/PSMA PET) and prior biopsy; these patients are scheduled to undergo salvage brachytherapy as part of routine clinical practice. A calculated sample size of 63 patients will be reached over a 2-year recruitment period. Follow-up will be conducted according to standard clinical practice every 6 months for the 4-year duration of the study.