Olivia Newton John is feeling ''positive and confident of total healing'' following her second breast cancer diagnosis.

The 'Grease' star has had to postpone her planned concert performances next month in the US and Canada after learning the life-threatening disease has spread to her sacrum, a bone in the lower back, but her close pal John Farnham says she believes her treatment will be successful.

John told News.com.au: ''I've spoken to Olivia in the last few days, and, as always she is very positive. She told me she is feeling good and confident of a total healing.

''The love and support from family and friends as well as people in general is enormous comfort to her.

''I've also spoken to Doctor Cebon at Olivia's Wellness facility, and he tells me that her positivity is a great asset to her and if anyone can beat this she can.''

Olivia, 68, was previously diagnosed with breast cancer 25 years ago in 1992 and underwent a mastectomy.

The 'Psychical' hitmaker - who has 31-year-old daughter Chloe with her ex-husband Matt Lattanzi - previously said fighting cancer ''taught her compassion''.

She said: ''I am grateful for the experience because without it I would not have done many of the things I have done in my life. It's taught me compassion for those going through difficult times.''

And a number of Olivia's showbiz pals reached out to the star after she revealed her breast cancer has returned.

Drag Queen RuPaul, 68, wrote on Twitter: ''Let's all send Olivia healing love energy @olivianj (sic)''

Pop star Sara Bareilles hailed the 'Grease' star ''the bravest'' for opening up about her battle with cancer for the second time.

The 37-year-old singer wrote on the micro-blogging site: ''My heart and prayers are with you @olivianj. You are the bravest and the strongest!! (sic)''

And Dolly Parton's sister Stella, 68, wrote: ''Will be praying you make a speedy recover. Sending lots of love. You are stronger than you know. (sic)''