Uh, I'm pretty sure no cancer researcher in the world is giving up on curing ALL cancers if they can. I mean, you automaticaly win the nobel prize for sure, get assured to be put on a stamp, and free drinks for the rest of your life if you "cure cancer." If you cure "just" one subtype of cancer, you probably get tenure or plenty of grant money, but you probably won't get automatically laid by saying "I'm the guy who cured multiple myeloma!" in a bar.
THIS is absolutely why I went into medicinal chemistry and worked on pancreatic cancer !!!!