Cancer is extremely complicated because it is caused by mutations over the course of ones life which results dysfunction of the basic and central cellular processes and which "escape" the normal control/repair mechanisms. Tons of things affect these systems and they are highly regulated. Cancers also actively evolve and contain many different kinds of cancer cells which react differently to compounds/drugs. The bottom line is don't believe anything 'prevents cancer' or 'cures cancer' until it has been shown in a double blinded population level clinical trial. Anything else is just an interesting finding that might lead somewhere.