PACE-A is a randomised phase III study comparing SBRT, or stereotactic body radiotherapy, with surgery for intermediate and low risk prostate cancer. The study was conceived when basically Da Vinci robotic prostatectomy was becoming much more widely used and SBRT was evolving as a treatment for prostate cancer. We thought it was important to try and compare these two treatments in a randomised study. It was difficult to do because difficult to randomise against surgery and therefore the numbers were relatively low, but we did successfully randomise 123 patients.
Patients were randomised on a 1:1 basis between SBRT and surgery. Surgery had to be robotically assisted or laparoscopic, it couldn’t be an open prostatectomy. SBRT was delivered initially only with CyberKnife but then as the study evolved it was delivered on Linac platforms as well.
The study randomised 123 patients; there were 60 in the surgical arm and 63 in the SBRT arm. We had two co-primary endpoints: we expected the urinary toxicity was likely to be a bit worse with surgery and likewise bowel toxicity was likely to be a bit worse with SBRT. So we designed it with two co-primary endpoints, the first was urinary continence, which was use of pads at two years, any use of pads, and then EPIC bowel bother, which is a toxicity measure, again at two years.
What we found was with surgery the use of pads was 46% at two years whereas with SBRT it was 4% so it was a highly statistically significant difference between the two. Likewise, with bowel bother on the EPIC scale the most you can get is 100 and for surgery patients scored 97, which is very good, and for SBRT 88.7. Again that was different between the two. Bowel rates were still very low in both arms so significant bowel complaints were very, very low.
We also compared sexual bother at two years and, again, for a full score you can get 100. On the surgical arm patients scored 27 and on the SBRT arm they scored 57. So that was, again, highly statistically significantly different and sexual function was much better with SBRT compared to surgery.
How can this impact the future treatment of prostate cancer?
The important thing for this study is that we have now got level 1 evidence of the different outcomes that we can expect with these two treatments. It’s important that patients are aware of it so when patients are making decisions about their treatment they should be aware of this data. Most of these men with intermediate or low risk prostate cancer treated are not going to die of prostate cancer and that’s really important. So if you take that out of the equation, that most of them will not die, then the side effects of the treatment are really important to their decision making. Understanding their risks, understanding the likely impact on their sexual function, likely impact on their continence and bowel function all should be taken into account when patients are making a decision about which treatment they want. Oncologists will find this data very useful. I hope the surgeons will find this data very useful and I hope patients will be better informed when they make their treatment decisions.
