RESUMEN
PURPOSE/OBJECTIVE(S): This study describes the pattern of failure in patients with biochemical (BCR) recurrence after low-dose-rate (LDR) brachytherapy as a component of definitive treatment for prostate cancer. METHODS: Patients with BCR after LDR brachytherapy ± external beam radiation therapy (EBRT) were enrolled on prospective IRB approved advanced imaging protocols. Patients underwent 3T multiparametric MRI (mpMRI); a subset underwent prostate specific membrane antigen (PSMA)-based PET/CT. Pathologic confirmation was obtained unless contraindicated. RESULTS: Between January 2011 and April 2021, 51 patients with BCR after brachytherapy (nâ¯=â¯36) or brachytherapyâ¯+â¯EBRT (nâ¯=â¯15) underwent mpMRI and were included in this analysis. Of 38 patients with available dosimetry, only two had D90<90%. The prostate and seminal vesicles were a site of failure in 66.7% (nâ¯=â¯34) and 39.2% (nâ¯=â¯20), respectively. PET/CT (nâ¯=â¯32 patients) more often identified lesions pelvic lymph nodes (50%; nâ¯=â¯16) and distant metastases (18.8%; nâ¯=â¯6), than mpMRI. Isolated nodal disease (9.8%; nâ¯=â¯5) and distant metastases (nâ¯=â¯1) without local recurrence were uncommon. Recurrence within the prostate was located in the transition zone in 48.5%, central or midline in 45.5%, and anterior in 36.4% of patients. CONCLUSION: In this cohort of patients with BCR after LDR brachytherapy ± EBRT, the predominant recurrence pattern was local (prostate ± seminal vesicles) with frequent occurrence in the anterior prostate and transition zone. mpMRI and PSMA PET/CT provided complementary information to localize sites of recurrence, with PSMA PET/CT often confirming mpMRI findings and identifying occult nodal or distant metastases.