After almost three decades, legislation around gene modification and editing technology is getting an overhaul.

After exhausting all the available options for treating his rare blood cancer in New Zealand, David Downs was told by his doctor to go home and make the most of the time he had left.

Then, assisted by a stroke of luck and a lot of fundraising, he took part in a gene-editing trial in the USA. Three weeks after the treatment, there was no sign of cancer in his body.

Last week, the government confirmed plans to end the country's nearly 30-year ban on genetically engineered and modified organisms outside the lab.

The reformed legislation will use Australian laws as a blueprint and include the establishment of a gene technology regulatory body, to ensure any developments won't impact human health or the environment.

In the wake of this announcement, Downs spoke to The Detail about his experience receiving life-saving gene editing treatment.

"The CAR-T cell therapy, from a patient's perspective, is very straight forward compared to the normal treatments. Chemotherapy is the normal treatment for blood cancer, that is essentially poison, you're putting poison in the human to try and kill the cancer cells. When you go to CAR-T cell therapy it's quite different because instead of trying to kill the cancer, it basically assists the immune system to do its job."

Downs says the idea behind the therapy is that while the immune system can fight infection naturally, it doesn't recognise cancer cells as dangerous, so CAR-T cell therapy essentially teaches the immune system to recognise and kill the cancer.

"My experience was going to get my blood taken out, which takes a few hours but it's not particularly difficult. Then they send that blood off to a laboratory, I wait about three weeks while those T-cells get genetically engineered and that's very precise. Then they send it back to me and I basically get one injection of my own blood," he says.

Downs says that once those genetically engineered cells are in his body, they recognise the cancer as a danger and destroy them.

"The little, tiny PAC-MEN are going around chomping away at the cancer cells," he says.

"When I went back, three or four weeks after the shot, they said that's it, there's no sign of cancer left in your body."…

Go to this episode on rnz.co.nz for more details