The back pain that Newton-John originally believed to be sciatica is instead breast cancer that has metastasized to the sacrum

Olivia Newton-John Is Battling Breast Cancer That Has Spread Into Her Back

Olivia Newton-John is putting her U.S. and Canadian tour on hold after discovering she has cancer, the singer announced on Facebook Tuesday afternoon.

Doctors have diagnosed the star, 68, with breast cancer that has metastasized to the sacrum, according to the statement. The star initially postponed the first half of her concert tour two weeks ago because of severe back pain from what she thought was sciatica; however, further tests discovered it was actually cancer that spread.

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“She plans to be touring in August. They’re all very positive,” a source close to the Grammy winner told PEOPLE on Tuesday about Newton-John and her family.

Earlier this month, daughter Chloe Lattanzi posted a message on Instagram asking for prayers. “I love u mama … Will all of u send healing prayers for my mamas back please,” she wrote May 17. “I believe in the power of positive thinking and energy. Love u all.”

Along with natural wellness therapies, the entertainer will be treated with a “short course of photon radiation therapy,” adds the statement. Newton-John is “confident she will be back later in the year, better than ever, to celebrate her shows.”

“I decided on my direction of therapies after consultation with my doctors and natural therapists and the medical team at my Olivia Newton-John Cancer Wellness and Research Centre in Melbourne, Australia,” says Newton-John in the statement.

A rep for Newton-John previously told PEOPLE the star is currently “resting and going through treatment.”

The star has been touring her inspirational album LIV ON, which is a personal collection of songs about overcoming trauma, including her bout with breast cancer in 1992 and the loss of her sister Rona to brain cancer in 2013.