A cancer expert says it's uncommon and "very unlucky" for breast cancer to return more than 20 years after an initial diagnosis, as is the case for Australian singer Olivia Newton-John.
Professor Sanchia Aranda, president of the Union for International Cancer Control and CEO of Cancer Council Australia, says cancer cells are "pretty tricky things" and can lie dormant in the body for many years.
"It is unusual but not unheard of, so it can happen," Prof Aranda said when asked about Newton-John's diagnosis.
"It's why chemotherapy is used after a person has an early breast cancer to try to mop up all of those cells but if we don't get them all then they can be there and undergo change later on," Prof Aranda said.
Newton-John had been battling back pain on her current US and Canadian concert tour.
The 68-year-old announced on her Facebook page on Tuesday the pain turned out to be breast cancer that has metastasised to the sacrum, a bone in her lower back, 25 years after her primary diagnosis of breast cancer.
"I decided on my direction of therapies after consultation with my doctors and natural therapists and the medical team at my Olivia Newton-John Cancer Wellness and Research Centre in Melbourne, Australia," she said.
The entertainer first battled breast cancer 25 years ago and has since used her own experience to promote awareness about the disease.
While the risk of breast cancer returning diminishes over time it never completely goes away, Prof Aranda said.
"We know that the risk is highest within the first two years," she said.
It is, however, very dependent on the individual, she noted.
Once the disease returns and has spread beyond the breast, five year survival drops from 95 per cent to around 25 per cent.
Being overweight, a lack of exercise and alcohol consumption all increase a woman's chances of breast cancer returning.
Evidence shows that even one drink a day substantially increases the risk of the disease returning, cautioned Prof Aranda.
"We are often seen as promoting the negative messages but it really is important to maintain a healthy lifestyle always but particularly after a diagnosis of breast cancer," she said.
Keeping your alcohol consumption very low, she says, will certainly help.
