The Da Ya Think I'm Sexy? hitmaker had an operation on his thyroid gland to remove a growth and the operation brought "the surgeon's knife within a fraction of an inch" from his vocal cords.

After the treatment, he lost his voice and had to relearn how to sing, and Stewart has now revealed his vocals will never be the same again.

He says, "It was a scary period. I couldn't sing for about three weeks. But the voice came back an octave down so I sing a little lower now than I used to. It was only because I had a CAT scan that it was spotted. If I had left it a couple of years it would have been a different story. I want to make people aware of early detection. I was lucky and it makes me want to tell everybody that they should get checked."

Stewart is now an active campaigner for U.K. charity The City of Hope Foundation, which seeks to find cures for all forms of cancer.