Good luck. I got a phone call to come in immediately after my biopsy results came out, although it was on the 2 week limit and I'd not had an MRI or bone scan.
It was positive but I wouldn't take that as a definite in all cases. I especially wouldn't take it the bone scan result was positive. I can guess you're worried as you say.
Such a large prostate can often be benign. There isn't a particular link with PCa and a very large prostate.
The advice I once got was to take each step at a time and not get ahead of yourself. The imagination is often worse than the event. Easier to say though.