Campbell was diagnosed with the cancer in 2013, which briefly went into remission only to return again. He received further treatment and cancer is once again in remission and he will be undergoing the stem cell transplant in an attempt to keep the cancer from returning once again.

He wrote on the band's official website, "As many of you know, I've been scheduled to start a stem cell transplant and as soon as I got home from tour I began the necessary tests and preparations. I'll be admitted to hospital soon for all the yucky bits, so in the meantime I'm headed to Target to stock up on cozy pajamas, fresh underwear, and a sackful of car-porn.

"Unfortunately, this means that I won't be able to perform with the band on the upcoming NFL broadcast on Sept. 28th, nor will I be able to do the shows scheduled for Oct/Nov.

"While I can't say that I'm looking forward to the process ahead, I'm very much looking forward to what I feel will be a most successful outcome. Next year will be very busy for Def Leppard with a new album and a world tour, and frankly, I don't think they would sound as loud without me, so I have no intention of letting the team down!