Just to clarify, as far as I can determine, apple seeds do not contain arsenic. Its a common mistake though. They do contain cyanide in small doses which is actually the bit that kills the cancer cells. It comes in the form of a molecule that also contains 2 other things that actually prevent the healthy cells from absorbing the cyanide but the cancer cells 'suck it up' and die.
But dont take my word for it.....do some research for yourself.
Its quite fascinating and shocking too!