Your comment answers itself. There is no such thing as "cancer, singular". It's a catch-all term for a wide range of conditions relating to uncontrolled tissue growth.

We have gotten a lot better at treating cancer, in general, literally because we've gotten a lot better at treating specific types of cancer. There are no "broader cases", only cases of specific cancers which we've either gotten really good at treating, or which we haven't gotten really good at treating yet.