A Doctor is a man, that looks at test, that were also made by man. They or anyone else can give a person a set time to die.
My grandfather had terminal cancer, his doctor suspected he had it for a while. Granddaddy, did not like to the doctor at all. The doctor gave him 6 months at the most.
I believe (this is just me thoughts on this) that a persons mind plays a great role in the responsive health of the body. Its like if you believe it so shall it be.
If your friend takes the doctors time of his ultimate demise. Then he/she will in fact die, at or before the doctors told him/her. But, if he/she gets into that strength that you didn't know you had you can prolong or even beat the cancer. Don't look at it as the cancer having you, you must have it and beat it.
I agree with pippap all of it, you must remain positive, you can turn some cancers around, and delay some.
You only have no more fight, when they lay you 6 feet under, or in a crypt or oven, depends on how you're going to go.
My grandfather, did pass, but not without a major fight. The doctor that gave him the date with death. Died 5 months after he told him. He lived a little over 7 yrs after the first doctor. The one he went to see after the first doctor passed, he also died car accident this was a year after wards, the first one heart attack. The third one, about 9 month after #2 had died. While on vacation went rafting, drowned. The last one is still alive he is my doctor now for last 10 years plus.
Your friend does need to get his house in order. Its a very good thing to do dieing or not everyone should have some type of will.
Never think you don't have anything, they are so easy to do, if a simple one. The more complex ones you may need an attorney.