Now, the singer has spoken out following her second diagnosis, as she recovers from her breast cancer relapse.
This past May, the four-time Grammy victor postponed US and Canadian tour dates and revealed to fans that she was battling breast cancer again, 25 years after her first diagnosis.
Fans were surprised and saddened earlier this year when Olivia Newton-John revealed she was suffering from a breast cancer relapse, but now the singer has sent out a video message to let her fans know she is "feeling great".
In the video, Olivia said: "Firstly, I'd like to express my gratitude to all of you who sent such kind and loving messages of support over the past few months".
"Your prayers and well wishes have truly helped me, and continued to lift my spirits", she continues.
"I'm feeling great and so look forward to seeing you soon", the beloved "Grease" star added brightly.
"Olivia is finishing her treatments and is excited to see her fans when she begins performing again next week".
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"The back pain that initially caused her to postpone the first half of her concert tour, has turned out to be breast cancer that has metastasized to the sacrum", read a statement on Newton-John's Facebook page.
She said: "I am really grateful for and touched by the worldwide outpouring of love and concern.
Thank you. I am feeling good and enjoying total support from my family and friends, along with a team of wellness and medical practitioners both here in the United States and at my Olivia Newton-John Cancer Wellness and Research Centre in Melbourne, Australia".
The star looks glowing and happy in the video, in which she announces the research centre's new campaign, called We Go Together.
Meanwhile, her daughter Chloe Lattanzi took to social media last month to give fans an update on her mother's health.
"I've had time to reflect on how proud I am of the center and the important contribution it makes to the lives of the communities it serves", Newton-John said.