"If you wait until the polyp becomes a cancer then the chance of curing that disease is much, much less," he said.
"If you pick it up much earlier you can remove the polyp that may have become a cancer, or you can remove a cancer that may then become unresectable [unable to be removed with surgery] and grow much faster."
Dr Arnold said often bowel cancer was only detected when it blocked an intestine, with a 50 per cent survival rate, or when it caused heavy bleeding.
Overseas screening programmes were proven to save lives and picked up conditions other than bowel cancer, he said.
While the national programme was aimed at people with no symptoms, it was expected word-of-mouth from the programme would encourage more people with symptoms to come forward.
Dr Arnold said the age of people targeted by the screening programme was yet to be determined. A trial in Auckland targeted people aged more than their mid 50s but nationally the age was likely to be older because there were not enough people to perform an endoscopy.
At present the procedure was performed by doctors in New Zealand but an Auckland pilot programme is underway to train nurses, as was the practice in Australia and Britain.
In May the Government allocated $39 million for the screening programme but HBDHB is funding the new building itself from operational savings.
HBDHB chairman Kevin Atkinson said the board originally approved a $9.7 million building but geotechnical issues delayed the project.
The delay coincided with a national construction boom and a $2 million price escalation.
Because the project exceeded $10 million the HBDHB was required to have the project approved by the Ministry of Health.
Mr Atkinson said Gemco Construction was awarded the contract to build the new facility.