Are you aware of some of David Icke's other claims?
Around 20 years ago he announced on a TV chatshow that he was the Son of God. He claimed the earth was about to be devasted by floods and tsunamis - didn't happen.
He claims there is a secret group of shape-shifting reptilian humanoids called the Babylonian Brotherhood, which created and controls humanity. They take human form and include the queen, Boxcar Willie, Kris Kristofferson and a host of other public figures who, he claims, all indulge in Satanic rituals, paedophilia, kidnapping of children, drug parties and murder which they need to satisfy the reptilian blood lust which allows them to retain their temporary human form.
He's also obscenely anti-semitic.
Best to take any of his theories with a pinch of salt
A particle of antimatter would annihilate the corresponding matter. Antiprotons would annihilate protons, regardless of where the protons are located. Actual anti-cancer would simply annihilate any matter it would come in contact with, whether it was cancer tissue or something else.
First of all.. cancer is not a virus. A virus is a living organism that replicates itself and releases toxins inside your body. Cancer is caused by a loss of the control of cell division.. a cancerous tumor is made up of cells just like every other part of the body.. but these cells are damaged so that they can not function properly and their replication control processes are "broken".. so they just keep on dividing. More specifically, cancer is usually caused by the loss of special genes that control cell division. The only way to restore normal tissue is to either kill the cells before they can grow any larger or restore the genes that control cell division. Therefore a drug that rid someone of cancer would have to accomplish one of these two tasks.