As I mentioned in some other post, it could be that the healing effects are either a) increased by a person's submissiveness to the Island or
b) deteriorate over time to cause the person even greater harm.

Or the entire story of cancer is bulls***!

__________________
"The Naked Gun!"

Frank Drebin remembers a lost love.

Frank: It's the same old story. Boy finds girl, boy loses girl, girl finds boy, boy forgets girl, boy remembers girl, girls dies in a tragic blimp accident over the Orange Bowl on New Year's Day.

Jane: Goodyear?

Frank: No, the worst.