Salvage low-dose-rate 125I partial prostate brachytherapy after dose-escalated external beam radiotherapy

Purpose: To report outcomes on 5 patients treated with salvage partial low-dose-rate (LDR) 125-iodine (I-125) permanent prostate seed brachytherapy (BT) for biopsy-proven locally persistent prostate cancer, following failure of dose-escalated external beam radiotherapy (EBRT). Material and methods: A retrospective review of the Fox Chase Cancer Center prostate cancer database identified five patients treated with salvage partial LDR I-125 seed implant for locally persistent disease following dose-escalated EBRT to 76-84 Gy in 2 Gy per fraction equivalent. All patients had post-EBRT biopsies confirming unilateral locally persistent prostate cancer. Pre-treatment, EBRT and BT details, as well as post-treatment characteristics were documented and assessed. Results: The median follow-up post-implant was 41 months. All five patients exhibited low acute genitourinary and gastrointestinal toxicities. Increased erectile dysfunction was noted in three patients. There were no biochemical failures following salvage LDR I-125 seed BT to date, with a median post-salvage PSA of 0.4 ng/mL. Conclusions: In carefully selected patients with local persistence of disease, partial LDR I-125 permanent prostate seed implant appears to be a feasible option for salvage local therapy with an acceptable toxicity profile. Further study is needed to determine long-term results of this approach.