Someone said back in the 70s that launching an Apollo like effort at curing cancer would be like launching that Moon effort without knowing anything about the laws of gravity. Even today our ignorance of cancer is a humbling reality.
The bottom line after billions of dollars spent- the best minds in the world trying to solve it- well over 50 years of serious effort is:
WE don't know what causes it,
We don't know how to prevent it,
we don't know how to cure it.
The best we do is elaborate treatments. -Tom