Salvage Low Dose Rate Prostate Brachytherapy: Clinical Outcomes of a Phase II Trial for Local Recurrence after External Beam Radiotherapy (NRG Oncology/xxxx).

We report efficacy of a prospective Phase II trial (YYYY) of salvage low dose rate (LDR) prostate brachytherapy (BT) for local failure (LF) after prior external beam radiotherapy (EBRT) with minimum 5- years' follow up.

Eligible patients had low/intermediate risk prostate cancer (PCa) prior to EBRT and biopsy-proven LF > 30 months after EBRT, with PSA < 10 ng/mL and no regional/distant disease. The primary endpoint, late GI/GU Adverse Events (AEs) (CTCAE V3.0 ≥ Grade 3) was 14%. With minimum 5-year follow up after salvage BT, secondary clinical outcomes including disease-free (DFS; includes death from any cause), disease-specific (DSS), and overall survival (OS) were estimated using the Kaplan-Meier method and modelled using Cox proportional hazards regression. Local tumor progression (LF), distant and biochemical failure (DF/BF) were estimated using cumulative incidence. Time to LF, DF and BF were modeled by cause-specific Cox proportional hazards regression.

From 05/2007 -01/2014, 20 centers registered 100 patients (92 analyzable). Median follow up is 6.7 years (range: 0.3-11.2); median age 70 years (range: 55-82); median prior EBRT dose 74 Gy (IQR: 70-76) at a median of 85 months prior(IQR: 60-119). Androgen deprivation was combined with salvage BT in 16%. 10-year OS is 70% (95% confidence interval [CI]: 58 -83). 19 patients died (5 PCa, 10 other, 4 unknown). 10-year failure rates are local 5% (95% CI:1-11), distant 19% (95% CI:10-29) and biochemical 46% (95% CI:34-57). DFS is 61% at 5 years; 33% at 10 years. No baseline characteristic was significantly associated with any clinical outcome.

This is the first prospective multicenter trial reporting outcomes of salvage LDR BT for LF after EBRT. Five-year freedom from BF is 68%, comparable to other salvage modalities. Although further LF is rare (5%), BF climbs to 46% by10-years.

International journal of radiation oncology, biology, physics. 2021 Nov 02 [Epub ahead of print]

Juanita Crook, Joseph P Rodgers, Thomas M Pisansky, Edouard J Trabulsi, Mahul B Amin, William Bice, Gerard Morton, Albert D Murtha, Eric Vigneault, Joelle Helou, Jeff M Michalski, Mack Roach, David Beyer, Ashesh B Jani, Eric M Horwitz, Adam Raben, Stephanie Pugh, Howard Sandler

Center for the Southern Interior. Electronic address: ., NRG Oncology Statistics and Data Management Center. Electronic address: ., Mayo Clinic., Kimmel Cancer Center, Thomas Jefferson University., University of Tennessee Health Science Center., Southwest Cancer Foundation., Juravinski Cancer Centre at Hamilton Health Sciences., Cross Cancer Institute., L Hotel-dieu De Quebec., Princess Margaret Hospital., Washington University., University of California San Francisco., Cancer Centers of Northern Arizona Healthcare., Emory University., Fox Chase Cancer Center., Christiana Care Health Services, INC. CCOP., NRG Oncology Statistics and Data Management Center.

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