Salvage low-dose-rate brachytherapy for local recurrences after prostatectomy and adjuvant or salvage external beam irradiation: Feasibility study on five patients and literature review.

Purpose: To assess the feasibility and tumor outcome of re-irradiation with low-dose-rate brachytherapy for macroscopic local recurrences after radical prostatectomy (RP) followed by adjuvant or salvage external beam radiation therapy (EBRT).
Methods and Materials: Between 2011 and 2018, five men with histologically proven local failure within the prostate (4) or seminal vesicle bed (1) after RP and adjuvant or salvage EBRT (median dose: 67.5 Gy) underwent a salvage brachytherapy (S-BT). The median delay after EBRT was 86 months (range 75-234). Two patients were castration-resistant at the time of S-BT. The gross tumor volume was defined on a multiparametric MRI and transrectal US imaging. Echo-guided transperineal implants of Iodine-125 seeds were optimized with a per-operative dosimetry and delivered with the seed-selectron.
Results: A high conformity was achieved with a high dose to the CTV (D _95%  > 145 Gy in all but one) and very low dose to the rectum, urethra, and bladder. With a median followup of 21 months, all but one patient experienced nodes and/or bone metastases. Local control was achieved in 3/4 of evaluable patients (local failure distant to the treated volume in one). To date, no Grade 2 or more late toxicities were observed.
Conclusion: For selected patients, focal local recurrence brachytherapy after PR and EBRT appears technically feasible and safe, but the efficacy remains uncertain as the majority of patients quickly relapsed at other sites. Large prospective studies are still required to better select patients who will benefit from this strategy.
(Copyright © 2021 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)