But the NBR rich-lister wasn't ready to die. He engaged one of Britain's top oncologists and cancer-cure researchers, Oxford-educated Professor Justin Stebbing, and undertook a gruelling regime of treatment to shrink the tumours. The treatment will not cure him but will buy time.
His oncologist recommended Keytruda and was one of the first in Britain to use it, while Sir Douglas was among the first patients to be treated for colon cancer secondaries with the drug.
He said he had two friends with melanoma who had been treated with Keytruda and both thought they were cured.
Sir Douglas is due back in New Zealand next week to spend Christmas with his children and grandchildren at the family's Matauri Bay farm.
He puts great faith in Professor Stebbing, and is financially backing a charity that helps to
fund his cancer research.
"He's the most published oncologist in Europe over the last three or four years. What he always says to me about claimed cancer cures is: it's the tumours you can't see that you've got to worry about.
"Luckily in my case I've got so many and so widely spread there's no chance it's anything but a life extension job."
The past two years of treatment has seen Sir Douglas suffer painful bowel blockages, severe dehydration, weight loss, exhaustion and peripheral neuropathy (numbness in his hands and feet as a result of the chemotherapy) which caused him to fall in front of car in London and stumble over an 18m cliff at Matauri Bay. But he puts up with it - he has no choice.
Sir Douglas is still actively involved in two major businesses, Chiltern International and Downtown Music Publishing, and has much to do, including making sure his children Jessica, Laura and Campbell are ready to take over the family fortune.
Chiltern International, a global clinical research organisation, has doubled in size and profit since the Myers family trust took over a controlling interest last year. This year, the company completed a $400 million takeover of an American company.
"It all looks pretty exciting and positive," Sir Douglas said. "Healthcare seems one of the fastest-growing industries around. We do pharma drug testing, so we are in the thick of it."
Downtown Music Publishing - which owns the US administration rights to some of the Beatles' singles, all of John Lennon's music after he left the Beatles and Yoko Ono's song catalogue - has "signed up some great talent and is now a recognised force in the business and opening offices around the world", Sir Douglas said.
"So, all in all a pretty good year and my children are growing in confidence, which is great."
• Keytruda is a breakthrough immunology drug used to treat patients with advanced melanoma and lung cancer.
• The government drug-buying agency Pharmac is refusing to fund Keytruda, deeming it a low priority.
• Melanoma patients face a bill of $300,000 to pay for it privately.
• Health Minister Jonathan Coleman says the Government will not overrule Pharmac over its decision.