Olivia Newton-John reveals sister's battle with cancer

Olivia Newton-John opened up about her older sister's cancer during an interview with ET online.

The "Grease" actress said her sister Roha had recently been diagnosed with brain cancer. She has decided to postpone her plans to relocate to Vegas to be with her family in this difficult time.

Earlier this month it was reported that Newton-John would move to Nevada to begin a series of performances at the Flamingo Hotel in Vegas.

"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," Newton-John told ET. "I want to thank everyone in advance for respecting our privacy during this difficult time."

The 64-year-old actress was diagnosed with breast cancer almost 20 years ago. She has been free of the disease after getting a mastectomy and undergoing treatment.