Abstracts Archive

UK & Ireland Prostate Brachytherapy Conference 2019

Abstract number 1

LDR versus HDR brachytherapy boost in prostate cancer patients – a retrospective analys 

Rodda S, Slevin F, Murray L, Bottomley D, Bownes P, Henry A
Leeds Cancer Centre, Leeds Teaching Hospitals NHS Trust 

Aims & Introduction: To report biochemical Progression Free Survival (bPFS) and toxicity in men with non-metastatic prostate cancer treated with LDR or HDR brachytherapy boost (BT) combined with external beam radiotherapy (EBRT). 

Materials/Methods: 287 men consecutively treated with combination of BT boost and EBRT from 1996-2012 from a single centre were evaluated retrospectively. Data was extracted from electronic records. 116 had LDR (I-125) BT to a dose of 110Gy in combination with EBRT 45Gy in 20 Fractions (LDR-EB) treated from 1996-2007. 171 had HDR BT (17Gy in 2 fractions or 15Gy in 1 fraction) in combination with EBRT 35.75Gy in 13 or 37.5Gy in 15 fractions respectively (HDR-EB) treated from 2007-2012. Duration of androgen deprivation was at clinician discretion. bPFS was defined by PSA nadir +2 and toxicity scored using RTOG. 

Results: Median follow-up was 74.1 and 57.0 months for LDR-EB and HDR-EB groups respectively. The LDR-EB group were slightly younger than HDR-EB group (63 versus 65 years: p=0.02) and had greater proportion of high risk disease (p=0.02). At 5 years there was a significant improvement in bPFS in LDR-EB compared to HDR-EB groups (90.5% vs. 77.6%, p=0.003). On multivariate analysis, Gleason grade ≥8 versus 6 (HR: 5.47) and treatment group LDR-EB versus HDR-EB (HR: 2.33) both predicted bPFS. 5-year cumulative incidence of G3 and above GU and GI toxicity was higher in LDR –EB (8% and 5%) compared to HDR-EB groups (4% and 1%) but was not statistically significant.

Conclusion: Risk of biochemical failure was more than double in men treated with HDR-EB compared to LDR-EB .There was higher grade 3+ GU and GI toxicity in the LDR-EB group although this did not reach statistical significance. LDR-EB may provide more effective PSA control at 5 years. Given its retrospective design and lack of randomisation, these results should be regarded as hypothesis-generating.