How to tell family

I have just been diagnosed with advancd PC. Will be starting ADT and Radiation soon. I have a 21 to son who is my life and my best friend. He has his own issoes being epileptic and almost drowning a while ago. I know that when I tell him, it will b very hard for him and I am worrid that h will not cop. His mother is tiotally NOT the caring type and all our extended family are in Perth. We are on the ast coast. How do I tell him? What do I say?