Well, yes, if the bone scan showed that the cancer had spread to your bones, it would then be incurable and you'd be looking at completely different treatment options intended not to cure your cancer, because that couldn't be done, but to extend your life as long as possible before the cancer killed you. Sorry to be grim, but that's the way it is.
However, with a PSA of 8 that is an EXTREMELY unlikely scenario. The bone scan is purely a routine part of diagnosis and it's almost certain to come back negative. You'll then be on a curative treatment path intended to get rid of the cancer and allow you to live a perfectly normal life. Don't be rushed into a decision. Make sure you talk to both a urologist about surgery and an oncologist about radiotherapy and other non-surgical treatments, and decide which is right for you.
Best wishes,
Chris