Hollywood actor Sam Worthington was forced to consider his own mortality after witnessing his mother's battle with ovarian cancer and his father's struggle with diabetes and heart problems.

The fiercely private Avatar star has opened up about the pain of watching his parents Ronald and Jeanne suffer, insisting the hellish experiences brought his family closer together.

He tells Australia's GQ magazine, "Mum's cancer battle struck at the heart of life and death for me. She said, 'I'm not going to let this disease control how I live'. I might not have agreed with the way Mum chose to handle her treatment at the time, but she taught me that the best way to help her was to stop being all 'woe is me', so we did, and everyone in our family got stronger by staying positive together...

"When I was young my parents were these titanic, infallible figures. But Mum's illness, and Dad's battles with diabetes and heart attacks had a ripple effect on me - reminding me of my own mortality and that these illnesses are genetic."

Worthington's mother has since beaten the illness, and the actor is encouraging his fans to join him in supporting Australia's annual White Shirt campaign, which raises money for the Ovarian Cancer Research Foundation (Ocrf).

He adds, "Self-awareness and early detection are key, so that's what we're encouraging with White Shirt Day: don't think twice, support the campaign on May 1 (14)."