Olivia Newton-John has decided to postpone her run of Vegas shows in order to spend time with her family, after discovering her sister has 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 in a statement. “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.”

The 64-year old actress and singer battled breast cancer 20 years ago and is now facing a tough road with her sister, Rona. Her Vegas residency was to begin soon at the Flamingo Hotel as a stand-in for Donny and Marie Osmond’s away dates, and though it’s believed she will eventually perform, nothing has been confirmed yet.

Rona was famously married to her sister’s “Grease” co-star, Jeff Conaway, for five years. They have a son together, 38-year old Emerson.