Olivia Newton-John postpones Vegas gig

Story originally appeared on USA Today.

Big sis, Rona Newton-John, has been diagnosed with brain cancer.

If you were hoping to see Olivia Newton-John on stage in Las Vegas in the coming months, you're out of luck.

The star has had to postpone her upcoming Flamingo residency substituting for Donny and Marie Osmond's away dates even before tickets had gone on sale and the official announcement had been made, reports the Las Vegas Sun.

Olivia, 64, has revealed to Entertainment Tonight that her big sister, Rona, has been diagnosed with cancer.

Olivia, who battled breast cancer 20 years ago, said in a statement that she had received the "very sad news" that Rona has 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."

She went on to say, "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. I want to thank everyone in advance for respecting our privacy during this difficult time."