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The guitarist announced he had been diagnosed with cancer earlier this year and the band was forced to change its tour plans to give him time to recover.
However, Iommi didn't want to be left out of the recording sessions for the band's new album, so the rockers moved their work from the U.S. to the U.K. to allow him to take part while undergoing treatment in his native Britain.
The rocker admits the recording schedule was dictated by his health, but the work helped him through the gruelling chemotherapy.
He tells Britain's Kerrang! magazine, "It was good for me to do that. I did feel tired and sick - and it does make you sick, you start throwing up. But on the days when I felt I could do it, we were all there working."
Bassist Geezer Butler adds, "(Iommi) was going to the hospital one day, and we'd go into the studio the next depending on how the chemo was affecting him."
Iommi rejoined his bandmates on stage last month for a small show in their hometown of Birmingham, England and the star is looking forward to the group's big gig at Britain's Download festival over the weekend.
He adds, "(The warm-up show) was great. Going through what I've gone through over the past year has been like living in a different world - being onstage and to get that (reaction from the fans) is just fantastic, it really boosts you up."
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