Due to the diagnosis, the heavy metal band have cancelled most of their forthcoming 2019 tour.
“I’ve been diagnosed with throat cancer. It’s clearly something to be respected and faced head on – but I’ve faced obstacles before. I’m working closely with my doctors, and we’ve mapped out a treatment plan which they feel has a 90 per cent success rate. Treatment has already begun,” Mustaine wrote in an Facebook post.
The recently announced “Megacruise” taking place between 13-19 October will take place as scheduled, “and the band will be a part of it in some form”, Mustaine wrote.
They will also continue to work in the studio on the follow-up to their 2016 album Euphoria, which Mustaine said he "can't wait for everyone to hear".
“I’m so thankful for my whole team – family, doctors, band members, trainers, and more,” Mustaine said. “I’ll keep everyone posted.”
Fans and fellow artists were quick to send messages wishing Mustaine the best with his treatment.
Anthrax’s Scott Ian said: “Please join me in sending all of our most powerful positive mind bullets to my brother Dave. You got this my friend, you can beat it – like you beat me in arm-wrestling! Kick its ass and get healthy!”
Mustaine’s Megadeth bandmate David Ellefson wrote: “Praying for my friend Dave Mustaine for a full and speedy recovery!”
Mustaine founded Megadeth more than 30 years ago, pioneering the sound that would become known as thrash metal.
He vowed that Megadeth would be "back on the road asap".