Slayer have been forced to cancel their Canadian tour dates with Megadeth, Machine Head and Suicide Silence because frontman Tom Araya has been admitted to hospital for urgent back surgery.It is unknown if Araya will be well enough to play their upcoming UK tour which kicks off in Nottingham on November 18."What is foremost in our minds right now is that Tom do whatever he needs to to get this taken care of,” said guitarist Kerry King. “While all four of us are disappointed that we won't be able to see through all of our commitments set for the next few weeks, the most important thing is Tom's health. Slayer's new album, World Painted Blood, is out this week.