Hi You must of course be guided by your consultants but if you are a genuine grade 3 ( no one can tell for certain unless it's removed,sliced and diced and looked at under the microscope or did it show some local spread on your MRI ) Lots of men with grade 3 seem to me at least to do better long term with the HT/ Radiotherapy route.
I've seen a fair few instances on this site of men who have opted for a prostatectomy turn out to have grade 3 then have to have HT/radiotherapy as well.( Can happen with Grades 1& 2 of course but less likely)
It's your choice of course if you decide not to be treated but what about your family. Would they support you in that decision? Do you really want to give in before you know whether you can have a long remission for a good many years?
As you were a safety expert in the nuclear industry how often is there an actual disaster?. I can only think of a couple off the top of my head( Chernobyl for one) but you will no doubt know of more and plenty of near misses. Most of the time things run according to plan so why do you think the disaster (serious side effects wise) will happen to you in particular?
As others have said life is a risk but how will you feel later on if your Pca does become advanced/ incurable/ terminal and you perhaps wish you had taken up the treatment offered.
Best wishes whatever you decide.
Ann