PO50 Presentation Time: 10:00 AM: Long-Term Results of Salvage High Dose-Rate Brachytherapy with or without Pelvic External Beam Radiotherapy in Patients with Palpable Local Recurrence of Prostate Cancer After Radical Prostatectomy

Abstract

<h3>Purpose</h3> This study aims to evaluate the long term outcomes and toxicities in patients with clinically apparent, gross local recurrence of prostate cancer after radical prostatectomy, treated with salvage high dose-rate brachytherapy (HDR-BT) with or without pelvic external beam radiotherapy (EBRT). <h3>Materials and Methods</h3> Retrospective chart review was performed to identify patients with clinically apparent, gross local recurrence of prostate cancer after radical prostatectomy who underwent salvage HDR-BT at a single institution between 2002 and 2020. HDR-BT regimens included 950 cGy x 2 (N=4), 1500 cGy x 1 (N=2), 950 cGy x 4 (N=1), and 800 cGy x 2 (N=1). Pelvic EBRT was allowed at the discretion of the treating physician. Treatment and clinical characteristics were obtained for each patient, and outcome and toxicity data were collected. Toxicity was graded according to Common Toxicity criteria for Adverse Events Version 5.0. Descriptive analysis was performed. <h3>Results</h3> A total of 8 patients were included in analysis with a median follow-up of 49 months (range: 9 to 223 months). Five (63%) patients presented with a biochemical recurrence, and 3 patients (38%) presented with symptoms including hematuria and urinary obstruction. Seven patients underwent TRUS-guided biopsy which confirmed recurrent adenocarcinoma. The remaining patient underwent a PSMA PET/CT scan revealing a PET-avid soft tissue lesion in the prostate bed, but declined biopsy and proceeded with treatment without pathologic confirmation. Median age at time of salvage brachytherapy was 68 years (range: 59 to 85 years). Median time from prostatectomy to salvage HDR-BT was 95 months (range: 19 to 207 months). Median PSA at time of HDR brachytherapy was 2.32 ng/ml (range: undetectable on ADT to 13 ng/ml). Median lesion size was 2.5 cm (range: 1 to 3.6 cm). Six patients (75%) received adjuvant pelvic EBRT, 45-50 Gy in 25 fractions. Seven out of 8 patients received ADT after salvage brachytherapy for a median duration of 12 months (range: 8 to 24 months). The remaining patient did not receive ADT due to cardiac comorbidities. Seven out of 8 patients were alive at last follow-up. There have been no locoregional recurrences. Three patients developed distant metastatic disease. One patient, who had negative conventional staging scans 3 months prior to brachytherapy, was found to have distant metastatic disease only 2 months after salvage brachytherapy and died due to metastatic prostate cancer 9 months after HDR-BT. The other 2 patients developed distant metastases at 14 and 27 months after brachytherapy. One patient developed late grade 3 urinary incontinence requiring artificial urinary sphincter (AUS) placement 18 months after brachytherapy. This patient had the largest tumor size, 3.6 cm in longest dimension, and received pelvic EBRT in addition to HDR-BT. He is now more than 10 years out from HDR-BT with undetectable PSA and doing well with his AUS. There were no other grade 2 or higher genitourinary or gastrointestinal toxicities. <h3>Conclusions</h3> This study demonstrates the long-term safety and efficacy of salvage HDR brachytherapy in the setting of clinically apparent local recurrence of prostate cancer after radical prostatectomy, with durable locoregional control and acceptable rates of toxicity. HDR-BT should be further explored as an option for dose-escalated salvage radiotherapy in patients with gross local recurrences after radical prostatectomy.