Can metastatic disease be cured?

This is certainly not a joking matter. Metastatic prostate cancer to multiple areas of bone cannot be cured presently. It may be controlled for a time as others have correctly answered. Cytotoxic chemotherapy - which was my specialty - is not very effective and may do more harm than good. Often hormonal therapy helps more. We all wish your grandfather the best. Remember that all doctors try to buy time for people. None of us lasts forever. The important thing is to buy quality time for people.