Comment Also it is the body attacking itself (Score 1) 366
That makes it harder to deal with.
What some people seem to forget is that we dealt with the easy stuff in medicine already. We are getting to tougher and tougher problems to tackle, hence why it takes longer and more research to deal with.
Cancer is very tricky. As you note it is a type of issue, not a single disease (much like the flu is a type of viral infection, not a single virus) and it really is the body turning against itself, it isn't an outside pathogen that can be dealt with.