Only around half of phase III trials show the approach being tested is better than the current standard, and often the improvements seen are quite small. It is rare to find an approach being tested has a substantial impact on mortality. So the PR07 trial results, which showed that adding radiotherapy to hormone therapy halved prostate cancer deaths among men with locally-advanced disease, stand out from the crowd.
PR07 recruited patients between 1995 and 2005. 1,205 patients from the UK and Canada took part in the trial. Each man had locally-advanced prostate cancer (cancer which had grown outside the surface of the prostate but had not spread further). Half were treated with hormone therapy and the other half were treated with a combination of hormone therapy and radiotherapy.
The long-term findings from the trial, after an average of eight years of follow-up, showed that the addition of radiotherapy to hormone therapy improved overall survival, and halved the risk of men dying from prostate cancer. For every 100 men treated with the approach, six extra would be alive after 10 years, compared to if they had been treated with hormone therapy alone.
These findings have changed clinical guidelines and practice around the world, which means many men are benefiting. A modelling study published in 2016 found that the increase in the proportion of patients in the UK treated with hormone therapy plus radiotherapy could result in around 3730-5177 extra life-years over 15 years from a cohort of 7930 men diagnosed in a single calendar year, compared to if all had been treated with ADT alone.
These results led to a change in the control arm of the STAMPEDE trial, which has since found ways of further improving survival for men with prostate cancer.
The PR07 trial registration number is ISRCTN24991896. The trial was coordinated by NCIC Clinical Trials Group, Ontario, Canada and MRC Clinical Trials Unit, London, UK.