Efficacy and toxicity outcomes for patients treated with focal salvage high dose rate brachytherapy for locally recurrent prostate cancer.

INTRODUCTION: Isolated local recurrence of prostate cancer following primary radiotherapy or brachytherapy may be treated with focal salvage high dose rate brachytherapy, although there remains an absence of high quality evidence to support this approach. METHODS: Men with prostate cancer treated consecutively between 2015 and 2018 using 19 Gy in a single fraction high dose rate brachytherapy (HDR) for locally recurrent prostate cancer were identified from an institutional database. Univariable analysis was performed to evaluate the relationship between patient, disease and treatment factors with biochemical progression free survival (bPFS). RESULTS: 43 patients were eligible for evaluation. Median follow up duration was 26 months (range 1-60). Median bPFS was 35 months (95% confidence interval 25.6-44.4). Kaplan-Meier estimates for bPFS at 1, 2 and 3 years post salvage were 95.2%, 70.6% and 41.8% respectively. On univariable Cox regression analysis, only nadir PSA was significantly associated with bPFS although the majority of patients were also treated with androgen deprivation therapy. Only one late grade 3 genitourinary toxicity was observed. CONCLUSION: Focal salvage HDR brachytherapy may provide good biochemical control with a low risk of severe toxicity. Further evaluation within clinical trials are needed to establish its role in the management of locally recurrent 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.

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.