Cancer may be difficult to cure once it starts growing. It is like saving a skyscraper once its demolition has started. I doubt cocaine could do the magic just like that. But I must say Yerba de Coca tea is delicious in Peru. And I did not notice any negative effects.

Also, not getting cancer is actually very easy. Just don't eat and don't drink sugars and carbohydrates. You only need not much fresh fruits and almost no seed/potato products. Water, meet, fish and eggs and not much vegetables (perhaps some every other day) should do it. And be happy. Cancerogenuous materials are still a thing, but if you live that life style, you are much much more resistent to them.