There are lots of rumors about Oliver Sykes and throat cancer. But as far as I can tell, they’re just rumors. The only references I can find to it online are in random discussion forums, and no one there gives any conclusive answers. I would think that if it were true there would be a legitimate news report about it somewhere, but I found none.
So I would say that if you’re worried about Oliver Sykes and throat cancer, don’t worry unless and until there’s some solid info to go on.