High-dose radiotherapy in patients with high-risk prostate cancers treated with long-term androgen deprivation...

For patients with high-risk prostate cancer, the role of dose-escalated radiotherapy in combination with long-term androgen deprivation treatment (ADT) is controversial, without any demonstrated benefit on cancer-specific or overall survival. We aimed to evaluate the effect of a 10 Gy dose increase, from 70 Gy to 80 Gy, on progression-free survival in men with high-risk prostate cancer.

In this multicentre, open-label, randomised, phase 3 trial, we enrolled patients with high-risk prostate cancer, defined as prostate-specific antigen of 20 ng/mL or more, Gleason score of at least 8, or clinical stage T3-T4, from 25 centres in France. Participants were randomly assigned (1:1) by minimisation, stratified by centre and previous pelvic lymph node dissection, to receive prostate-targeted dose-escalated external beam radiotherapy (80 Gy; 2 Gy per fraction for 8 weeks) or standard-dose external beam radiotherapy (70 Gy; 2 Gy per fraction for 7 weeks), combined with long-term ADT. Neither the participants nor the investigators were masked to the allocated treatment. The primary endpoint was 5-year progression-free survival defined as the time from randomisation to first biochemical (defined as prostate-specific antigen >nadir plus 2 ng/mL) or clinical (ie, local, regional, or metastatic) disease progression, analysed in the intention-to-treat population, with 197 events required. 5-year progression-free survival was the prespecified endpoint, and 10-year progression-free survival was additionally reported (post hoc) in view of the low number of events at 5 years. The trial is registered at ClinicalTrials.gov, NCT00967863, and is complete.

Between April 6, 2009, and Jan 24, 2013, 505 patients with high-risk prostate cancer were enrolled; 250 were assigned to receive dose-escalated radiotherapy (80 Gy) and 255 to receive standard dose radiotherapy (70 Gy). All participants were male and ethnicity data were not collected. At a median follow-up of 9·5 years (IQR 8·5-10·3), 5-year progression-free survival was 91·4% (95% CI 87·0-94·4) in the dose-escalation group versus 88·1% (83·2-91·6) in the control group, and 10-year progression-free survival was 83·6% (77·8-88·0) versus 72·2% (65·3-78·0; stratified HR 0·56, 95% CI 0·40-0·78, p<0·0001). Grade 3 or worse adverse events assessed at 6 months (acute toxicity) were observed in 60 (24%) of patients in the dose-escalation group and 62 (25%) in the control group. The most frequent grade 3 or worse adverse events were sexual disorders (28 [11%] in the dose-escalation group vs 20 [8%] in the control group) and bladder or urethra disorders (12 [5%] vs 19 [8%]). Adverse events assessed at 5 years (late toxicity) occurred in 118 (70%) of 168 in the dose-escalation group and 122 (73%) of 168 in the control group; grade 3 or worse late toxicities occurred in 19 (8%) participants in the dose-escalated radiotherapy group versus 17 (7%) participants in the control group. The most common late grade 3 adverse event was bladder or urethra disorders (seven [4%] vs three [2%], respectively). Serious adverse events occurred in nine (4%) patients in the dose escalation group and nine (4%) in the control group; none were considered to be treatment related. There were no treatment-related deaths.

For patients with high-risk prostate cancer, radiotherapy at a total dose of 80 Gy, in combination with long-term ADT, improved progression-free survival and could be a potential option in this situation. However, given the low number of events, further research is needed to consolidate and confirm the benefit in dose-escalation in prostate cancer-specific survival and overall survival.

French National Cancer Institute and AstraZeneca.