Hi fionag
It may be that you have not received replies from men treated with Cyberknife because it is not widely used in the UK as of yet, at least within the NHS where most men here have treatment. There are also a few private facilities that use this treatment here. It is yet another way of administering radiotherapy externally but in a more precise way. Therefore, I would think that potential side effects would be similar to those of those having a form of External Beam, say like IMRT or IGRT but the oncologist is best able to advise on this. We did have a man 'Roy', who had Cyberknfe or something similar to it (there are a number of more advanced machines now for dispensing RT). He had this as salvage treatment due to the cancer spreading to a rib and it did eradicate this tumour. Unfortunately, a tumour has since been found in a rib on the other side but there is no more NHS funding for him to have this treated too, even if it was considered appropriate. So in short, Cyberknife can be effective on specific targets, provided they are not many, but once the cancer is taking hold in several places, it becomes increasingly beyond the scope of Cyberknife to safely/effectively treat.