Advice from the Class?

So I have a personal problem, that is sort of related to our class, and I was hoping that people in the class could help me, and give me some advice on what I should do. Let me start by saying that my Papa (my grandfather) is an extremely important person in my life. While my mother was going to school full time and working full time, my Papa was the one that took care of me and raised me. Even though I am now 22 years old, every week Papa will show up at my door step with groceries, and things he thinks I "need". There has not been a day that has gone by that my Papa doesn't try to help me in anyway possible. Everyone is my family knows that Papa and I have a special connection. That is why my family has kept from me that Papa has been sick, and was diagnosed with prostate cancer. I have noticed that Papa was getting thinner, but every time I asked him if things were okay, he assured me they were. I guess my grandfather wanted to tell me, alone, when he was ready. This news completely destroyed me. I tried to remain calm in front of him, but as soon as I was in my apartment, I just couldn't stop crying. My Papa went back for more tests a few weeks ago, and they found out that the cancer as also spread to his bones. The worst part about this whole situation is that Papa is refusing to go through radiation or chemotherapy. My whole life Papa has been there for me and taken care of me, and I feel like it is my turn to try to take care of him. I want to tell him that I think he is making a huge mistake by not going through with treatment options. But I feel like that is not my place. I just get upset because we read about people, like Henrietta Lacks, who didn't have much control of her options, and what the doctors did to her. Papa actually has options, and I feel like he is choosing the wrong one. I would like an opinion from the class, do you think I should push my Papa to go through with treatments, or let him do what he wants? If I push him, would I be just like every other doctor we have read about that tries to influence their patients? Thank you for your advice in advance.