I'm Aliza, a Breast Cancer patient and the site's unofficial resident Medical Librarian. Med Librarians offers answers - usually to non medical questions, but we also offer referrals to doctors, hospitals, institutions, agencies, websites, books, media, etc. and research when requested or required.
Each person who's afflicted with Cancer (as long as they're an adult and they're of sound mind) has the right to choose whether to be treated (or not). I know this isn't necessarily news you want to hear as you cannot force your Dad to be treated. You can try to persuade him, of course, but ultimately the decision is his.
I often suggest that regardless of treatment options, that anyone diagnosed with Cancer contact the folks at CancerCare. The diagnosis is frightening in and of itself, and the Social Workers there offer great help to Cancer patients with their highly specialized needs as well as their caregivers. It's not like "regular therapy"! If your father's not up for speaking with them, I'd recommend that you call them anyway to apprise them of the situation and get their take of how to deal with it from your perspective-not only how to cajole your Dad into having treatment but how to help you cope in the event he definitely decides to not go through treatment. As you know, often treatment isn't for the faint of heart and I don't know how old your Da is or what other health conditions he has (only his oncologist could make these decisions with him). I think the CancerCare Social Workers will also be helpful to you in finding a way for you to be supportive of his decision not to have treatment- whether you agree with him or not this is important for both of you).
I know these are difficult times for you and I empathize. My late father had Chronic Lymphocytic Leukemia and though he treated it for 6 years, there came a point where the chemo treatments weakened him and secondary infections just got too much for him and he didn't want to go through anymore even though the rest of us weren't ready to lose him. It's a tough thing to deal with!!
f there's anything else that I can do to help you or you'd like to chat with me further offline, feel free to message me here or email me offline.