Olivia Newton-John is fighting cancer again. The singer has been forced to postpone her June tour dates in the United States and Canada in order to undergo radiation treatments.

Newton-John originally canceled her May tour dates due to what she thought was sciatica; however, as a Facebook post explains, "the back pain that initially caused her to postpone the first half of her concert tour has turned out to be breast cancer that has metastasized to the sacrum." In plainer terms, Newton-John's breast cancer has spread to her sacrum, a triangular bone in the lower back, situated between the hipbones.

"In addition to natural wellness therapies, Olivia will complete a short course of photon radiation therapy and is confident she will be back later in the year, better than ever, to celebrate her shows," Newton-John's Facebook post reads. "There will be no interview requests accepted at this time as Olivia’s focus is on her treatment and healing."

According to Newton-John, she decided on a combination of natural wellness therapy and photon radiation therapy to treat this cancer after consulting with her doctors, natural therapists and the team at the Olivia Newton-John Cancer Wellness and Research Centre in Melbourne, Australia, which opened in 2012. Newton-John has been an advocate for cancer awareness since being diagnosed with breast cancer in 1992; at that time, she underwent a partial mastectomy and breast reconstruction before being declared cancer free.

Those with tickets to Newton-John's affected tour dates can contact their show's venue directly to inquire about refunds. Rescheduled tour dates will be posted at OliviaNewton-John.com in the coming weeks.

Newton-John is, of course, best known as Sandy in 1975's movie version of the musical Grease, but in the early '70s, she earned accolades at the ACM Awards and CMA Awards; she also has two country Grammy Awards trophies to her name. Newton-John has recorded almost 30 albums throughout her career.

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