What does it mean when you dream of someone going to die of cancer?

Dreams communicate through symbols and metaphors. "Cancer" might represent something "eating at you," that is, a persistent problem that is draining one's energy and defies solution. It could represent a relationship that is getting progressively worse or a job that feels as if it is "killing you." However, dreams can be influenced by changes in the physical body, so if the dreamer has not had a physical checkup recently, it would not be a bad idea to get that done.