Key Points:

The Government is funding its Herceptin extension directly through the Health Ministry, rather than drug funding agency Pharmac.

National pledged during the election campaign to extend funding for the drug for Her-2 positive breast cancer from nine weeks to 12 months and Prime Minister John Key today confirmed that and released details.

Pharmac had refused to fund more than a nine-week course saying scientific and other information had failed to convince it that the longer course offered any additional benefits over the nine-week treatment it did fund.

Former Health Minister David Cunliffe said he could not overrule Pharmac.

The new Government has got around that by funding the extension through the ministry.

In a statement Pharmac said it helped the ministry in its negotiations with supplier Roche and by providing information.

"Pharmac fully respects the democratic process that has led to the Government's decision to fund 12-month treatment with Herceptin," the statement said.

The nine-week course would continue to be funded through Pharmac.

Mr Key said the 12-month course funding was backdated to November 19 when the government was sworn in.

Women who paid for Herceptin treatment privately between then and now could seek reimbursement from the ministry.

"The Government expects that over time, up to 300 women a year will benefit from the year-long course."

Health Minister Tony Ryall said the extension would be funded from the Government's planned $180 million new money for pharmaceuticals over the next three years.

Patients receiving a privately funded course of 12 months Herceptin now have the option of completing the remainder of their treatment with a public provider, where it will be fully funded by the Government.

Women who choose to continue receiving treatment privately will only be funded for the cost of the drug and not the delivery.

Patients who recently completed a publicly funded nine-week treatment or recently discontinued a private 12-month course of Herceptin treatment may now be able to receive the balance of a 12-month course of treatment publicly depending on their specialist's clinical judgment.

Mr Ryall said more patients would attend outpatient clinics and extra staffing would be needed in the long-term.

The Government would provide additional funding up to $3.6 million per annum to support the additional costs of administering the drug. The cost of the drug was not being released for commercial sensitivity reasons.

Mr Ryall said the benefits of using Herceptin to treat early breast cancer were well-known and recognised internationally.

The benefits of Herceptin have been reported in a number of international randomised trials and 34 other countries offer 12 months Herceptin as the standard of care.

Clinical trials found Herceptin had a small risk of significant side effects, such as heart failure, and that this risk may be increased with longer courses. Specialists and women would take that into consideration.