Olivia Newton-John diagnosed with cancer for third time

Grease star Olivia Newton-John has said she will "win over" her cancer.

The 68-year-old is using medical marijuana to help treat her cancer after being diagnosed with it for the the third time in three decades.

The four-time Grammy winner, who will turn 70 on September 26, told Australian news programme Sunday Night that doctors found a tumour in her lower back in 2017.

Newton-John said she is "treating it naturally and doing really well".

The singer said that for the pain, she is taking cannabis oil, made from marijuana her husband grows in California.

She told 'Sunday Night': "They (marijuana) help with pain, they help with sleep, so I'm very lucky that I live in a state where it's legal and that I have a husband that is a medicine man, how luck is that."

She has undergone radiation treatment and has cut sugar out of her diet.

The star said: "I believe I will win over it."

She said she hopes her native Australia will legalise medical marijuana.

Newton-John was first diagnosed with breast cancer in 1992, undergoing a partial mastectomy and reconstruction.

She was diagnosed with breast cancer again in 2013.