The guitarist was diagnosed with lymphoma, a blood cancer which develops in the lymphatic system, in 2011 and has undergone extensive chemotherapy and radiation treatment as part of his battle with the disease.
He has now revealed he was diagnosed with the illness in 2011 after spotting a lump in his groin during a book tour, and he has revealed his bandmate Osbourne pushed him to seek medical treatment during Black Sabbath rehearsals.
Iommi tells Guitar World magazine, "The diagnosis came when I was doing my book tour before we starred rehearsal (with Black Sabbath). On the book tour, I saw a doctor because this lump appeared in my groin. We thought it was just a swollen gland, so he gave me antibiotics. After the book tour, I was going to L.A to start rehearsals. He said if it wasn't gone in two weeks when I got there, I should see another doctor. So I did, because it was still there. He gave me more antibiotics, because I had developed an infection from this other problem I had with my prostate.... But it never went away.
"So we were rehearsing and writing, and I kept feeling this pain down in my groin. And Ozzy kept saying, 'You don't look really well.' And I'd say, 'Well, I don't feel too good.' He also told me to go get it checked out. I was going back to England to have the prostate operation, so I decided just to wait until then. They said they'd take out that other lump while they were in there. I thought nothing of it at all, but they found out it was cancer."
Iommi goes on to reveal he later received messages of support from cancer survivor and shamed cyclist Lance Armstrong, as well as late Deep Purple star Jon Lord, who died in 2012 after a battle with the disease.
He adds, "I got so many nice letters and messages from fans saying, 'You'll be okay. Just hang in there!' Even Lance Armstrong sent me a letter. And when Jon Lord was ill, before he passed away, I would get messages from him, saying, 'Look, if there's anything I can do to help with the treatments, just ask.' It really does help and makes you want to fight more."