The drug-buying agency Pharmac is under the spotlight over the lack of public funding for an effective treatment for advanced melanoma.
It has given a low priority to funding the drug Keytruda, saying it is highly expensive and more evidence of effectiveness is needed.
Keytruda is the brand name of a new immunotherapy drug, also known as pembrolizumab. It is given by infusion in hospital and is designed to enable a person's own immune system to target and destroy cancers.
Pharmac says Keytruda is effective in one third of patients and that two thirds do not benefit, but this is disputed by cancer specialists who say Keytruda causes major shrinkage of tumours in one third of patients, but a further third also get some shrinkage of their tumours.
Pressure continues to mount however, with patients presenting a petition signed by 11,000 people to Parliament yesterday.
Health Minister Jonathan Coleman has pledged more money for Pharmac in the upcoming Budget, and has soothed patients' worries by saying he believes a taxpayer-funded treatment for the deadly form of skin cancer is "on the way".
Pharmac chief executive Steffan Crausaz told RNZ's Health Correspondent, Karen Brown, in an exclusive Insight interview in February why it was demanding more data on Keytruda, or pembrolizumab.
Mr Crausaz said the advice Pharmac was receiving from oncologists was that Keytruda should be funded, but with a low priority.
"We're not quite sure how well it works in the long run, we're not quite sure if it really delivers on survival gains and also there's questions about affordability and other things."
He said the discussion was not only about Keytruda, but a number of drugs in the same class of treatments that were both available and becoming available in coming months.
Mr Crausaz said the data about one of these, nivolumab, or Opdiva, could offer Pharmac important insights into how the drugs work and how well over the long term.
Medical specialists estimate 20 to 30 people are paying for Keytruda themselves, at a cost of about $200,000 to $250,000 a year.
It's estimated about 200 to 300 patients with advanced melanoma may benefit from the drug if it were funded.