ASCO 2016
Hypo-fractionation of prostate cancer radiotherapy
Dr Charles Catton - Princess Margaret Cancer Centre, Toronto, Canada
I’m here today to present the results of an international randomised trial comparing two radiation fractionation schedules for men with intermediate risk prostate cancer. This is a trial that was sponsored by the Ontario Clinical Oncology Group and 27 centres in Canada, Australia and France have participated and we’re quite excited to present our results here.
Could you tell us those results?
The purpose of the trial was to compare a four week course of radiation treatment to a standard eight week course of radiation treatment. We hypothesised that the radiobiology of prostate cancer would allow us to compress the treatment into a much shorter treatment course. The concern there was that we would have more toxicity from the larger dose per fraction radiation. So we then used very conformal radiation treatment techniques to reduce the risk of toxicity. The trial was commenced in 2005 and we now have a median six years of follow-up, a maximum of ten years of follow-up. We were very delighted to find that our experimental regimen was non-inferior to the standard regimen in terms of an endpoint that we called biochemical clinical failure. This endpoint is a compilation of PSA failure or clinical failure or death from any cause, whichever one happens first. At five years the BCF control rate was 79% for both treatment arms and the survival curves did not diverge out to ten years. We were able to say that our short treatment arm was non-inferior to the standard treatment arm. More importantly, we did not see any increased toxicity with the short treatment arm, in fact when we looked at grade 2 GI toxicity there were fewer late grade 2, grade 3 and grade 4 events with the short treatment arm than the standard so at least in terms of late GI toxicity there appeared to be an advantage to the hypofractionation treatment arm. So we feel that we have demonstrated that a short course of four weeks of radiation should be the new standard for treating men with intermediate risk prostate cancer.
You mentioned the results from the numbers side, have you got any feedback from the patients, how it has affected their quality of life?
That’s a very good question. We looked at quality of life as part of the trial, it was one of our secondary endpoints. In terms of the EPIC scores, the SF-12 scores or the AUA toxicity scores we did not see any difference between the two treatment arms. So in this we looked at baseline, 24 months and 48 months, so at least for these time intervals we did not see any disadvantage to hypofractionation, which is what we call the short treatment course, for quality of life.
I imagine being able to get through the course much quicker and not have to make plans for eight weeks, eight months was…
Eight weeks.
You must be able to get a lot more done with your life.
And this was the whole point behind the study. Radiation takes a lot out of people’s lives in coming to treatment each day, finding transport, taking time off work and if we can have that it is going to make their lives substantially easier. There’s an added benefit, of course, in that we are essentially doubling the capacity of the healthcare system to provide treatment for these men.
And this was for intermediate risk prostate cancer, are there any plans to branch out to other risk factors or to other tumours?
There has been another study done looking at low risk prostate cancer that was very recently presented at a meeting last autumn. It showed very similar results so it does appear that by using modern radiotherapy techniques we can compress treatment safely for prostate cancer. We are not certain whether the radiobiology works for high risk prostate cancer and these studies are ongoing and have to be demonstrated to adopt that. Everyone is interested in hypofractionation for various very obvious reasons and it has been examined in breast cancer and in lung cancer and I imagine in other disease sites as well.
