Thrash metallers Slayer have announced they're postponing upcoming Canadian and American tour dates so lead singer Tom Araya can have back surgery.

"Tom gave various medical treatments more than a fair shot," said Slayer's manager Rick Sales in a press release, "but they just haven't handled the problem, so he's biting the bullet and is scheduled for back surgery at the end of this month."

This will bum metalheads who were hoping to see the legends out with Megadeth.

Slayer's March and April dates in Europe are off as well, though their dates in June and beyond are still technically on.

This isn't the first time Slayer have had to reschedule tour dates this year. Their Canadian Carnage tour with Megadeth — which was to take place in December — was rescheduled to March and April when Araya had back surgery for the first time in November.

Araya apparently started experiencing problems on the band's Australian/New Zealand/Japanese tour last October, when he was diagnosed with cervical radiculopathy, a "dysfunction of the nerve root in the spine," according to eMedicine, that's often caused by heavy manual labour, smoking, or driving and operating vibrating equipment.

The surgical procedure that Araya will undergo is called an anterior cervical discectomy with fusion.

"As unfortunate as this is for so many people — the Megadeth and Testament camps, the concerts' promoters, and, of course, the fans — Tom's health is the number one priority, and this has to happen," said Sales.