"Anastacia has sadly been diagnosed with breast cancer for the second time after having successfully survived her 2003 battle with the disease," a message on her website said Wednesday.
"Consequently she has been forced to cancel all performances, tours and any travel from now until further notice," the message said. "Anastacia was excited about her forthcoming European tour which was due to start April 6 in London. ... Please respect her need for privacy during such a trying time."
"I feel so awful to be letting down all my amazing fans who were looking forward to [my] 'It's a Man's World Tour.' It just breaks my heart to disappoint them," the singer said in a statement.
Anastacia's website said she plans to continue writing and recording songs for her new album despite her diagnosis and hopes to schedule a new tour as soon as possible.
The recording artist did not say what kind of treatment, if any, she planned to undergo.