If you have been involved with a Terminal cancer patient step on in...
I've been through this business twice. First off, my condolences for you, your friend, and this situation. There is nothing about cancer that doesn't suck.
My first go round was with my MIL. She was fine, then started coughing and couldn't stop. She goes to the doctor and finds out she has lung cancer. Six weeks later she was gone. It was a hard deal for the entire family as it happened so fast.
A few years later my wife was diagnosed with breast cancer. We did all the surgical, chemo, and radiation treatments but none of it did any good. She was in a three year slide until it finished eating her up. In my case, I had a good idea well ahead of time my wife was a likely candidate for cancer, but that didn't make it any easier to deal with. It was horrible. Knowing what was coming was like watching a train wreck in slow motion. You know what's going to happen, and all you can do was watch. You can't affect anything to improve the situation.
In your case with your friend, there are no good answers. So if I tell my hubby I'm sick, then I have him go through the grinder knowing I'm in bad shape? Or should I not tell my hubby to help shield him from this horror that can't be stopped? It's a shitty deal either way. Tell your friend to try hard not to be angry. There are no right or good answers to this situation. Only varying levels of lousy answers. There is no good way to lose your people. :(