External beam radiation therapy with or without low-dose-rate brachytherapy: Analysis of favorable and unfavorable intermediate-risk prostate cancer patients

A Systematic Review of the Efficacy and Toxicity of Brachytherapy Boost Combined with External Beam Radiotherapy for Nonmetastatic Prostate Cancer

CONTEXT

The optimum use of brachytherapy (BT) combined with external beam radiotherapy (EBRT) for localised/locally advanced prostate cancer (PCa) remains uncertain.

OBJECTIVE

To perform a systematic review to determine the benefits and harms of EBRT-BT.

EVIDENCE ACQUISITION

Ovid MEDLINE, Embase, and EBM Reviews-Cochrane Central Register of Controlled Trials databases were systematically searched for studies published between January 1, 2000 and June 7, 2022, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Eligible studies compared low- or high-dose-rate EBRT-BT against EBRT ± androgen deprivation therapy (ADT) and/or radical prostatectomy (RP) ± postoperative radiotherapy (RP ± EBRT). The main outcomes were biochemical progression-free survival (bPFS), severe late genitourinary (GU)/gastrointestinal toxicity, metastasis-free survival (MFS), cancer-specific survival (CSS), and overall survival (OS), at/beyond 5 yr. Risk of bias was assessed and confounding assessment was performed. A meta-analysis was performed for randomised controlled trials (RCTs).

EVIDENCE SYNTHESIS

Seventy-three studies were included (two RCTs, seven prospective studies, and 64 retrospective studies). Most studies included participants with intermediate-or high-risk PCa. Most studies, including both RCTs, used ADT with EBRT-BT. Generally, EBRT-BT was associated with improved bPFS compared with EBRT, but similar MFS, CSS, and OS. A meta-analysis of the two RCTs showed superior bPFS with EBRT-BT (estimated fixed-effect hazard ratio [HR] 0.54 [95% confidence interval {CI} 0.40-0.72], p < 0.001), with absolute improvements in bPFS at 5-6 yr of 4.9-16%. However, no difference was seen for MFS (HR 0.84 [95% CI 0.53-1.28], p = 0.4) or OS (HR 0.87 [95% CI 0.63-1.19], p = 0.4). Fewer studies examined RP ± EBRT. There is an increased risk of severe late GU toxicity, especially with low-dose-rate EBRT-BT, with some evidence of increased prevalence of severe GU toxicity at 5-6 yr of 6.4-7% across the two RCTs.

CONCLUSIONS

EBRT-BT can be considered for unfavourable intermediate/high-risk localised/locally advanced PCa in patients with good urinary function, although the strength of this recommendation based on the European Association of Urology guideline methodology is weak given that it is based on improvements in biochemical control.

PATIENT SUMMARY

We found good evidence that radiotherapy combined with brachytherapy keeps prostate cancer controlled for longer, but it could lead to worse urinary side effects than radiotherapy without brachytherapy, and its impact on cancer spread and patient survival is less clear.

Outcomes of Patients With Unfavorable Intermediate-Risk Prostate Cancer Treated With External-Beam Radiotherapy Versus Brachytherapy Alone

BACKGROUND

The NCCN Guidelines for Prostate Cancer currently recommend several definitive radiotherapy (RT) options for men with unfavorable intermediate-risk (UIR) prostate cancer: external-beam RT (EBRT) plus androgen deprivation therapy (ADT) or EBRT plus brachytherapy boost with or without ADT. However, brachytherapy alone with or without ADT is not well defined and is currently not recommended for UIR prostate cancer. We hypothesized that men treated with brachytherapy with or without ADT have comparable survival rates to men treated with EBRT with or without ADT.

METHODS

A total of 31,783 men diagnosed between 2004 and 2015 with UIR prostate cancer were retrospectively reviewed from the National Cancer Database. Men were stratified into 4 groups: EBRT (n=12,985), EBRT plus ADT (n=12,960), brachytherapy (n=4,535), or brachytherapy plus ADT (n=1,303). Inverse probability of treatment weighting (IPTW) was used to adjust for covariable imbalances, and weight-adjusted multivariable analysis (MVA) using Cox regression modeling was used to compare overall survival (OS) hazard ratios (HRs).

RESULTS

Relative to EBRT alone, the following treatments were associated with improved OS: EBRT plus ADT (HR, 0.92; 95% CI, 0.87-0.97; P=.002), brachytherapy alone (HR, 0.90; 95% CI, 0.83-0.98; P=.01), and brachytherapy plus ADT (HR, 0.78; 95% CI, 0.69-0.88; P=.00006). Brachytherapy correlated with improved OS relative to EBRT in men who were not treated with ADT (HR, 0.92; 95% CI, 0.84-0.99; P=.03) and in those receiving ADT (HR, 0.84; 95% CI, 0.75-0.95; P=.004). At 10-year follow-up, 56% and 63% of men receiving EBRT and brachytherapy, respectively, were alive (P<.0001). IPTW was used to determine the average treatment effect of definitive brachytherapy. Relative to EBRT, definitive brachytherapy correlated with improved OS (HR, 0.90; 95% CI, 0.84-0.97; P=.009) on weight-adjusted MVA.

CONCLUSIONS

Definitive brachytherapy was associated with improved OS compared with EBRT. The addition of ADT to both EBRT and definitive brachytherapy was associated with improved OS. These results suggest that definitive brachytherapy should be considered as an option for men with UIR prostate cancer.

A comparison of outcomes for patients with intermediate and high risk prostate cancer treated with low dose rate and high dose rate brachytherapy in combination with external beam radiotherapy

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Superior biochemical progression free survival for LDR in combination with EBRT.

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On multivariable analysis, HDR and EBRT and Gleason ≥8 predicted for progression.

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Low cumulative incidence of ≥grade 3 GU and GI toxicities.

Introduction

There is evidence to support use of external beam radiotherapy (EBRT) in combination with both low dose rate brachytherapy (LDR–EBRT) and high dose rate brachytherapy (HDR–EBRT) to treat intermediate and high risk prostate cancer.

Methods

Men with intermediate and high risk prostate cancer treated using LDR–EBRT (treated between 1996 and 2007) and HDR–EBRT (treated between 2007 and 2012) were identified from an institutional database. Multivariable analysis was performed to evaluate the relationship between patient, disease and treatment factors with biochemical progression free survival (bPFS).

Results

116 men were treated with LDR-EBRT and 171 were treated with HDR–EBRT. At 5 years, bPFS was estimated to be 90.5% for the LDR–EBRT cohort and 77.6% for the HDR–EBRT cohort. On multivariable analysis, patients treated with HDR–EBRT were more than twice as likely to experience biochemical progression compared with LDR–EBRT (HR 2.33, 95% CI 1.12–4.07). Patients with Gleason ≥8 disease were more than five times more likely to experience biochemical progression compared with Gleason 6 disease (HR 5.47, 95% CI 1.26–23.64). Cumulative incidence of ≥grade 3 genitourinary and gastrointestinal toxicities for the LDR–EBRT and HDR–EBRT cohorts were 8% versus 4% and 5% versus 1% respectively, although these differences did not reach statistical significance.

Conclusion

LDR–EBRT may provide more effective PSA control at 5 years compared with HDR–EBRT. Direct comparison of these treatments through randomised trials are recommended to investigate this hypothesis further.

Results of 15 Gy HDR-BT boost plus EBRT in intermediate-risk prostate cancer: Analysis of over 500 patients

PURPOSE/OBJECTIVE

To report biochemical control associated with single fraction 15 Gy high-dose-rate brachytherapy (HDR-BT) boost followed by external beam radiation (EBRT) in patients with intermediate-risk prostate cancer.

MATERIALS AND METHODS

A retrospective chart review of all patients with intermediate-risk disease treated with a real-time ultrasound-based 15 Gy HDR-BT boost followed by EBRT between 2009 and 2016 at a single quaternary cancer center was performed. Freedom from biochemical failure (FFBF), cumulative incidence of androgen deprivation therapy use for biochemical or clinical failure post-treatment (CI of ADT) and metastasis-free survival (MFS) outcomes were measured.

RESULTS

518 patients met the inclusion criteria for this study. Median age at HDR-BT was 67 years (IQR 61-72). 506 (98%) had complete pathologic information available. Of these, 146 (28%) had favorable (FIR) and 360 (69%) had unfavorable (UIR) intermediate-risk disease. 83 (16%) received short course hormones with EBRT + HDR. Median overall follow-up was 5.2 years. FFBF was 91 (88-94)% at 5 years. Five-year FFBF was 94 (89-99)% and 89 (85-94)% in FIR and UIR patients, respectively (p = 0.045). CI of ADT was 4 (2-6)% at 5 years. Five-year CI of ADT was 1 (0-3)% and 5 (2-8)% in FIR and UIR patients, respectively (p = 0.085). MFS was 97 (95-98)% at 5 years. Five-year MFS was 100 (N/A-100)% and 95 (92-98)% in FIR and UIR patients, respectively (p = 0.020).

CONCLUSION

In this large cohort of intermediate-risk prostate cancer patients, 15 Gy HDR-BT boost plus EBRT results in durable biochemical control and low rates of ADT use for biochemical failure.