Olivia Newton-John Reveals Sister's Cancer Battle

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After battling breast cancer herself, singer Olivia Newton-John is coming to the aid of her older sister, who has been diagnosed with brain cancer.

The 64-year-old "Grease" star, who beat breast cancer 20 years ago, has postponed her upcoming Las Vegas show to be with her sister, Rona Newton-John, 69.

In a statement to Entertainment Tonight, Olivia Newton-John said she had recently received "the very sad news" that her sister had been "diagnosed with brain cancer."

"In light of this news, I have decided to postpone my forthcoming Las Vegas residency to spend time with her and our family," Newton-John wrote. "As a cancer 'thriver' myself, as many people are, I am very aware of the importance of love, support and family during this journey she is about to begin."

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The Australian pop singer is postponing her gig at Vegas' Flamingo hotel substituting for Donny & Marie Osmond's away dates even before tickets go on sale, according to the Las Vegas Sun.

Her sister Rona was also an actress and was married to Newton-John's "Grease" co-star Jeff Conaway from 1980 to 1985. Their son, Emerson, 38, is a race-car driver.

Conaway, who famously struggled with substance abuse, appearing on "Celebrity Rehab with Dr. Drew," died in 2011 at age 60.