Multiple randomised trials of external beam radiation alonerrr and a meta-analysis which included brachytherapy boostr have demonstrated improved biochemical relapse free survival when treatment doses were escalated beyond 70Gy. The MDACC RCT comparing dose escalation from 70Gy to 78Gy reported 6 year freedom from failure increasing from 64% to 70%.r Most benefit was demonstrated in men presenting with PSA levels > 10. However, dose escalation via EBRT resulted in markedly increased rectal toxicity.r
Dose escalation via Brachytherapy boost
There are limited RCTs comparing the use of HDR + EBRT and EBRT alone. The study by Hoskin et alr compared HDR brachytherapy + EBRT with EBRT alone reported improved biochemical relapse-free survival in all groups. Mean PSA relapse-free survival in the HDR arm was 5.1 years vs 4.3 years EBRT alone, however, the control arm of the trial was with EBRT doses of 55Gy/20 fractions, is now considered too low.
Other randomised and non-randomised studies have also shown a biochemical control benefit to a brachytherapy boost.
An Australian matched pair analysis of 688 patients compared 344 patients treated with EBRT (46Gy/23 fractions) and HDR boost (19.5Gy/3 fractions) to 344 propensity score matched controls.r 5 and 10 year biochemical control was 70.9% and 32.8% vs 79.8% and 69.2% in the EBRT alone and EBRT + HDR cohorts respectively (HR 0.59, P=0.0011).
A large retrospective study (870 patients) from MSKCC compared patients treated with modern dose-escalated EBRT alone to 86.4Gy (470 patients) to patients treated with combination EBRT and brachytherapy boost (400 patients) and found a significant improvement in biochemical control at 7 years, 81.4% with EBRT alone and 92.0% with EBRT + brachytherapy.r
Fig. 2. Kaplan–Meier survival curves for patients free of biochemical and/or clinical failure and overall survival.
Solid line: external-beam radiotherapy plus high-dose-brachytherapy boost (EBRT + HDR-BTb). Dashed line: external-beam radiotherapy alone (EBRT). Number of patients at risk is shown against each time interval.
© Hoskin et al, 2012r