Just an aside--it's a little different when an immunotherapy is giving you sepsis. Actually a lotta different. How do you "stop" the effects? Can't just cut off the chemo. Think about that.
I think quality of life is very important and makes it easier for people to have hope and maintain a positive attitude while fighting the disease. I don't know that there has been any scientific studies of how much a person's outlook can affect their immune system but I believe it can be substantial. I know from watching family members who had to deal with cancer that its awful hard to have a positive outlook when you wake up sick every morning and see your hair falling out.