The long-term results of the RT01 trial, which looked at whether standard or higher doses of radiotherapy were best for treating localised and locally-advanced prostate cancer, were published in the Lancet Oncology on 26 February 2014.
The trial compared a 7.5 week course of radiotherapy (giving 74 Gy of radiation in total) with a 6.5 week course of radiotherapy (giving 64 Gy of radiation). The results show that, 10 years after treatment, men who had the higher dose of radiotherapy were less likely to have signs of their cancer coming back or getting worse. 55 per cent of men in the higher dose group had no signs of their disease getting worse, compared to 43 per cent who had the standard dose.
Men who received the higher dose were also less likely to need to start treatment with long-term hormone therapy within 10 years.
However, the trial found that there was no difference in how long men treated with the higher or standard doses lived. Men in both groups of the trial lived much longer than expected. Almost three quarters of men in the study were still alive after 10 years. Only 91 out of the 236 deaths that did happen were due to prostate cancer.
Men who received the higher dose were more likely to have side-effects from the radiotherapy, such as diarrhoea or rectal bleeding. However, most side-effects were mild or moderate, and few men had severe side-effects.
Professor David Dearnaley, of The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, who lead the study, said: "Our study has proved that treating men with localised prostate cancer using higher doses of radiotherapy is more effective than a less intensive regime. The dose-escalated regime is safe in the long term, and reduces the chances that a cancer will return and men will require further hormone-deprivation treatment. The side-effects of hormone treatment do need to be balanced against those of the extra radiotherapy doses, but overall our study has shown men are better off after having the escalated regime, as is now the norm in the UK.
Another key finding to come out of our study is that radiotherapy in general is both a safe and an effective treatment for localised prostate cancer. Almost three quarters of men treated with either the more or less intensive radiotherapy regimes are still alive after 10 years, and of the men who have died, less than half actually died from prostate cancer.
Further refinements in radiotherapy techniques since our trial began have made treatment even safer and are very important as men with localised prostate cancer have such favourable long-term survival prospects."
Matthew Sydes, Senior Scientist and Statistician at the MRC Clinical Trials Unit at UCL, said: "The RT01 trial has already changed how men with localised prostate cancer are treated. The current NICE guidelines recommend the use of the higher dose of radiotherapy, based on the five-year results of RT01. The trial also helped to develop guidelines on how to limit the radiation that organs near the tumour receive, and helped hospitals across the UK to introduce quality-assured conformal radiotherapy. It is now contributing to biological studies to help better understand the disease and the side-effects of radiotherapy."