Pop princess Kylie Minogue has been ordered by medics to cancel part of next year's (08) world tour over fears for her health. The singer, 39, was forced to pull out of her Showgirl tour in 2005 after being diagnosed with breast cancer. Minogue recently launched her comeback by announcing a tour to mark her 40th birthday next year - but doctors are advising against it. A source tells British newspaper the Daily Express, "Kylie is determined to do this tour. She was upset that she had to pull out of her last one - the Showgirl tour - when she received her cancer diagnosis. "If it was up to her, she'd do an endless string of dates but doctors say she needs to make herself the priority and take more time out to relax. "They just don't think travelling so much to perform each night is a good idea. Knowing Kylie, she will want to push herself. But she just can't as much as she used to."