Yes. If the cancer gets out of the prostate, the cells can migrate and usually settle on the bones where they continue to grow. Your friend would have had a bone scan to check if the cancer had migrated, but if it was spotted early enough, chances are it is still confined to the prostate
Most of the prostate cancers are so slow growing that they never spread to other parts of the body and the patient dies of "old age" before the cancer spreads.
Some prostate cancers, the minority thank goodness, are extremely aggressive and do spread to other parts of the body.