Composer Andrew Lloyd Webber, 61, has been diagnosed with prostate cancer.
His spokesman said in a statement that the condition was currently in its very early stages, the BBC reports.
"Andrew is now undergoing treatment and expects to be fully back at work before the end of the year," the statement said.
Lord Lloyd Webber is best known for his musicals which include Evita, Starlight Express and The Phantom of the Opera. He composed Jesus Chris Superstar and Joseph and the Technicolor Dreamcoat.
Earlier this month, he launched his new musical Love Never Dies, a sequel to Phantom of the Opera, which is due to open in February next year.
He owns seven London theatres, including the Theatre Royal Drury Lane and the London Palladium.