I agree with Annie - go and see him and talk to him.
My mum died from advanced breast cancer. We were very close, but she was in Leeds and I was in London, so getting up to see her was difficult, especially as, when she was having chemotherapy, we were advised not to see her, in case we passed on any infection to her.
In the end, she died very suddenly from an infection, only a few weeks after being told that her cancer had returned and spread. I got the chance to see her, the day before she died, but she was already very ill from multiple organ failure, and was pretty much out of it. As I said, we were very close, so there was no 'unfinished business' between us, IYKWIM, but it still makes me sad that we didn't have any opportunity to talk about her, her illness, what she wanted to happen when she died (as she knew by then that her cancer was terminal.)
It sounds, though, like you may have some things that you need to deal with/talk about with your dad, and I would really recommend that you try and do that sooner rather than later.
So sorry for you. It's a bastard disease.