Sheryl Crow is wishing Olivia Newton-John ''the best'' following her cancer diagnosis.

The 'First Cut Is the Deepest' hitmaker - who underwent a lumpectomy and radiotherapy in 2006 after she found out she had non-invasive breast cancer - has reached out to the 'Grease!' star after she announced she has metastatic breast cancer that's spread to her sacrum - 25 years after she first fought the disease - and told her to stay strong spiritually and mentally in order to get through the ordeal.

Speaking to 'Entertainment Tonight', she said: ''I've only met her maybe once, and I love her. I have a lot of respect for her. I was a huge fan, and still am a fan. So I'm wishing her the best. Olivia, I didn't know this but I know how strong you are and how spiritual you are and I know you're on top of your health. I'm wishing you the best.''

The 55-year-old singer - who found out she had a benign brain tumour in 2011 that doctors are monitoring - wants to encourage people to look after their health.

She explained: ''I'm constantly telling people, particularly women because I have a very big female fan base, 'Make sure and know your family history and make sure and be diligent about getting your mammograms. Until we have a cure, early detection is the best we have.''

Meanwhile, Olivia is ''confident'' her cancer battle will be a ''positive success story''.

She said in a statement recently: ''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 US and at my Olivia Newton-John Cancer Wellness and Research Centre in Melbourne, Australia. I'm totally confident that my new journey will have a positive success story to inspire others! Love and light, Olivia.''

And the 'Physical' singer, 68, is already feeling better after undergoing a short course of photon radiation therapy and other natural treatments.