But through a twist of fate, he was given the opportunity to receive life-saving treatment in the US.
He managed to get on a clinical trial for a therapy which took the immune cells - known as the T cells - out of his body and genetically engineered them into "killer cells" before inserting them back into the blood.
Despite having to travel 15,000km, pay nearly $1 million and be away from his family at the most critical time, it saved his life.
The 47-year-old must return to the US every two to three months for check-ups but, while his doctors can't say he has been cured, every test shows no sign of cancer.
"Being told that was like getting a second chance at life," he said.
For Downs, a big part of that is paying it forward.
Not only has he been an advocate for a number of cancer sufferers desperate to be put on the same trial, earlier this year he went a step further and made a pledge to fundraise $1million to help get the same kind of treatment in New Zealand.
For the past 18 months, the Malaghan Institute has been working towards launching New Zealand's first clinical trial for the treatment and Downs has been raising thousands to help make it happen.
Head researcher Robert Weinkove previously told the Herald there were about 50 New Zealanders with non-Hodgkin's lymphoma who became terminal every year.
"CAR-T therapy won't work for all of those patients but there is a lot of research suggesting the therapy could be used to treat other diseases as well as lymphoma and leukaemia."
Weinkove said this was extremely exciting stuff that opened the door for many more studies.
"Rather than having everything made overseas, we are actually manufacturing almost from scratch locally in New Zealand that gives us a flexible platform to allow us to generate other types of CAR-T cells therapies in the future."
Thanks to Downs' fundraising efforts, as well as Freemasons New Zealand who donated $600,000, clinical trials are expected to start next year.
Don't miss it:
Tomorrow: Father with rare disease swims in a bid to raise $150,000.
Wednesday: Former Olympian, now tetraplegic starts multi-million dollar charity.
Thursday: Father with bowel cancer raises funds in a bid to change the stigma.
Friday: Limbless man becomes advocate for Mobility Dogs.