Olivia Newton-John Reveals Sister's Cancer Battle

Actress Olivia Newton-John speaks exclusively to ET, confirming that her older sister Rona has been diagnosed with brain cancer.

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Earlier this month it was reported that the Grease star would begin a residency in Las Vegas, performing at the Flamingo hotel. Now in the light of her sister's health news, Olivia will be postponing those engagements to be with her family.

"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," says Olivia, 64, who was diagnosed with breast cancer close to 20 years ago. "I want to thank everyone in advance for respecting our privacy during this difficult time."

Olivia has been free of the disease since undergoing treatment and a mastectomy.