Sam Neill has written a heartbreaking note for his children after being diagnosed with cancer

Sam Neill says he has written a note to his children and grandchildren amid his battle with stage three cancer.

The Jurassic Park actor has been battling angioimmunoblastic T-cell lymphoma.

He received chemotherapy for the disease for three months, however the treatment stopped working.

Doctors then pivoted and gave him a rare anti-cancer drug, which are infusions every fortnight and they have started to show positive results.

Neill has been in remission for 12 months.

However, he admits that this approach will likely fail in the coming years and he's 'prepared' for that eventuality.

"I'm not in any way frightened of dying. That doesn't worry me. It's never worried me from the beginning, but I would be annoyed," he said to the ABC.

"I'd be annoyed because there are things I still want to do. Very irritating, dying. But I'm not afraid of it."

The infusions are pretty brutal on his body and he admits to feeling like he's gone 10 rounds with a boxer once they're done.

But he tries to not focus too much on that and prefers to enjoy the time he has left.

"I know I've got it, but I'm not really interested in it," he explained to Australian Story.

"It's out of my control. If you can't control it, don't get into it."

Neill says he has around 10 days in between the infusions where he 'could not feel more alive or pleased to be breathing and looking at a blue sky'.

When he was first diagnosed, he reflected on his own mortality and what this will mean for his family.

As a result, he decided to write down his life in a letter that will be addressed to his children, according to the Daily Mail.

"I didn't know really how long I had to live," he said.

"And I thought yeah, I should probably write something down for my children and my grandchildren because I may not be here in a couple of months and it would be good for them to have a sense of me and and some of the things that I've done."

Neill also told the BBC that he started writing his memoir to 'give me a reason to get through the day'.

"I thought I need to do something, and I thought, "Shall I start writing?'" he said.

"I didn't think I had a book in me, I just thought I'd write some stories. And I found it increasingly engrossing.

"A year later, not only have I written the book - I didn't have a ghostwriter - but it's come out in record time."

He says that working on the book has provided him with a fresh perspective.