Andrew Lloyd Webber has been re-admitted to hospital after developing a "chronic infection" following surgery for prostate cancer.
A statement on the theatre impresario's website said that although the operation was a success, the infection needs immediate treatment.
His spokesmen said last month that the cancer was in its early stages and he hoped to return to work before the end of the year.
But an update on his website said he now hoped to be back in the New Year.
The statement, placed there last night, said: "Andrew has been re-admitted to hospital tonight following his operation for prostate cancer.
"He has been advised that while the operation was entirely successful, he has developed a post-operative 'chronic infection' which needs immediate treatment. He still hopes to be back at work in the New Year."
Lord Lloyd-Webber, 61, is best known for his musicals, which include Joseph And The Amazing Technicolor Dreamcoat, Jesus Christ Superstar, Evita, Starlight Express and The Phantom Of The Opera.
Last month, the composer launched the long-awaited sequel to Phantom, Love Never Dies, at Her Majesty's Theatre in London. The new musical is scheduled to open in March.
Phantom, which has been seen by some 100 million people worldwide, opened 23 years ago.
Prostate cancer affects around 35,000 men in the UK each year and kills just over 10,000.
The disease is the most common cancer in British men, accounting for a quarter of all new cases.Reuse content