A drug to treat cancer only has to be taken by people diagnosed with that cancer, for as long as they're diagnosed with it. A drug to prevent cancer has to be taken by everyone at risk for the cancer (which might be the entire population), for as long as they're at risk (likely decades). Hence, a treatment drug can be expensive and can have some nasty side-effects, while a prevention drug would have to be cheap with minimal side-effects. That's a much tougher constraint to work under.
Yep. This is basically the same problem we have with Alzheimer's - the people you need to treat are healthy people. The FDA just won’t let you test anything with any danger in healthy people. Since all new treatments inherently have risk it is basically impossible to give a new drug or treatment to healthy people.
Even giving something like metafomin [1] where we have decades of knowledge is in practice impossible to give to healthy people. No new treatment stands a chance.
