Int J Radiat Oncol Biol Phys 2021 Nov 03
Salvage Low-Dose-Rate Prostate Brachytherapy: Clinical Outcomes of a Phase 2 Trial for Local Recurrence after External Beam Radiation Therapy (NRG Oncology/RTOG 0526).
Abstract
Purpose
We report efficacy of a prospective phase 2 trial (NCT00450411) of salvage low-dose-rate (LDR) prostate brachytherapy (BT) for local failure (LF) after prior external beam radiation therapy (EBRT) with minimum 5-years' follow-up.
Methods and materials
Eligible patients had low/intermediate risk prostate cancer (PCa) before EBRT and biopsy-proven LF >30 months after EBRT, with prostate-specific antigen <10 ng/mL and no regional/distant disease. The primary endpoint, late gastrointestinal and genitourinary adverse events (Common Terminology Criteria for Adverse Events v3.0) grade ≥3 were 14%. With minimum 5-year follow-up after salvage BT, secondary clinical outcomes including disease-free survival (DFS; includes death from any cause), disease-specific survival, and overall survival (OS) were estimated using the Kaplan-Meier method and modelled using Cox proportional hazards regression. Local tumor progression (ie, LF), distant failure (DF), and biochemical failure (BF) were estimated using cumulative incidence. Time to LF, DF, and BF were modeled by cause-specific Cox proportional hazards regression.
Results
From May 2007 to January 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 [interquartile range (IQR):70 - 76] at a median of 85 months prior (IQR 60-119 months). Androgen deprivation was combined with salvage BT in 16%. Ten-year OS is 70% [95% confidence interval (CI) 58% - 83%]. Nineteen patients died (5 PCa, 10 other, 4 unknown). Ten-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 and 33% at 10 years. No baseline characteristic was significantly associated with any clinical outcome.
Conclusions
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% by 10 years.
Related Questions
What urethral dose constraints would you use off-trial for reirradiating the prostate using SBRT?
The short answer to this question is that there is no evidence-based answer. Below is a review for anyone interested. Background: The recognition of local recurrence as a pattern of failure seems to be growing, perhaps in part due to the increased utilization of advanced imaging (as previously discu...
Would you offer salvage radiation for a local recurrence of prostate cancer that was initially treated with SBRT?
At this time, I’m not sure there is enough data to recommend a course of re-irradiation after primary SBRT outside of a clinical trial, although I do know some who offer it. The majority of the data regarding re-irradiation for local recurrence after RT comes from smaller retrospective reports, alth...
Would you ever consider focal brachytherapy treatment in a patient who have in-prostate recurrences after RT?
Yes, our preference is focal treatment for unilateral disease on imaging (PSMA, PET, and MRI) and concordant biopsies. Our data suggest that this is just as effective as whole gland treatment for recurrences with possibly less toxicity. For patients b/l recurrent involvement after prior radiation tr...
Has use of PSMA PETCT revealed increased local failures than previously known after definitive prostate EBRT with biochemical failure?
Prior to the advent of PET imaging, the published rates of local recurrence (LR) after definitive RT vary widely in phase III trials from ≈ 1% (e.g., PCS IV) to ≈ 30% (e.g., PROG 9509). The heterogeneity is likely explained by several factors including (1) differences in baseline risk of local recur...
After definitive prostate RT, when do you prescribe ADT for local salvage (EBRT, HDR, LDR)?
For patients with localized recurrence after definitive radiotherapy, re-irradiation without ADT is a reasonable course of action and the one I usually favor. There are no current clinical trials that have been reported to demonstrate the benefit of ADT in this setting, but this practice is consiste...