Depends who the person is, and what the probabilities involved are.
I actually received a “terminal cancer” diagnosis 8 years ago, and took steps to survive it; and many factors including my distrust of the incentives within the medical system, my training in biochemistry and statistics, my concern for the welfare of my wife and children, limited how much I was prepared to spend on myself. And I had reasonable confidence that I could get a positive outcome on relatively small expenditure (vegan diet and high dose vitamin C – which in my particular case seems to have worked).
If it was my own life, and there were very high probabilities (both of my death, and the efficacy of the mitigation strategy) then I would probably do so. Similarly for someone I cared a great deal about.
And the question actually points to a much deeper issue in our society, which is that the needs of the money system vastly outweigh the value of individual human lives. And that is something we need to change quite quickly, as exponential technology is fundamentally altering the strategic landscape that made markets a relatively positive force in our history, and are turning the whole concept of exchange based values into an existential level threat – but very few people understand enough about strategic complexity to have much of an understanding about it.