Not if the cancer is terminal. At that point therapies might buy some time, but many terminal cancer patients don't want to drag it out, they WANT to die.
There are lots of diseases that are terminal, at least as far as modern medicine is concerned. For example, Alzheimer's, the one I mentioned. Doctors can try to slow the onset of the symptoms but other than that, there's nothing anyone can do. The patient gets worse and worse until they eventually die.
There is always some chance of survival though
I've heard that on rare occasions cancer can go into remission by itself. Nobody knows why, but that really isn't the point -- the wishes of the patient are what's important. To keep someone in that condition alive against their wishes is selfish.
My best friend's mother, who I knew all my life, had uterine cancer at age 85, went through one round of chemo, and was so sick she wanted nothing more to do with any of it; she wanted to die. So she did a short while later.
My own mother wanted to die, although she didn't really have a terminal illness. My father had died 2 years previously and she started rejecting food, she simply did not want to eat, and she finally told us she just wanted to die. She was 86, and did die a few weeks later.
We could have easily kept her alive by having a feeding tube put in, but she didn't want that, she wanted to die. That was the toughest decision me and my sisters had ever made, but we knew we had to honor her wishes. To go against them was to be selfish on our part. WE
wanted her alive, but she didn't want to be.
So that was that. It's not all about what science is capable of, or what the odds are of someone making it -- the patient's wishes must come first.