Brain metastasis

You start too many threads, BOSE - it makes it difficult to track replies.

To your question, the chance of PCa going to bone is very high unless it is diagnosed early and treated. In your dad's case the chance was 100% since he does have bone spread already. If this is a typo and you were asking about the chance of spread to the brain and / or skull, this is more likely with some types of prostate cancer than others. As your dad has skull mets, it may be that he has a more rare type. You could ask his doctor.