Almost $30,000 has been donated towards treatment for a West Auckland detective and mum battling incurable cancer.

Detective Sarah Cato, 35, was diagnosed with breast cancer four years ago.

After undergoing a mastectomy she found out that the cancer had spread throughout her body and was metastatic, or incurable.

Since her diagnosis Cato has undergone chemotherapy and radiation and has been taking Herceptin to slow further cancer growth.

But the five-year survival rate for metastatic breast cancer is only 22 per cent and Cato wants to do everything she can to stay alive as long as possible for her daughter, Emma, and wife, Keely, and to keep fighting crime.

Cato wants to try the drug Perjeta, which when used in conjunction with Herceptin has been shown to reduce the risk of metastatic cancer worsening.

Pharmac fully funds the drug but only for patients who have not been previously treated with Herceptin or chemotherapy.

Cato now needs $130,000 - at least - so she can get Perjeta.

The money will cover the initial course of the drug, at a cost of about $70,000, and ongoing infusions that cost up to $5000 each month.

On Thursday Cato shared her plan to raise money for Perjeta with the Herald.

Since then more than $27,000 has been donated by individuals, families, groups and businesses across New Zealand and overseas.

More than $20,000 has been donated into an account for Cato and when her Givealittle page was set up a further $6000 was paid by generous Kiwis.

"I am overwhelmed with the support from the public," Cato told the Weekend Herald.

"I feel very special and grateful that people are spreading the word and digging into their pockets. There is good karma floating all around."

Cato and her Waitematā police colleagues are planning a fundraiser function later this year with a silent auction and the donations are also rolling in for that.

A number of local musical groups have offered to entertain during the night and businesses have offered a range of items to auction off including sporting goods, homeware, wine, luxury accommodation, art, photography services and whiteware.

One local business donated its weekly gold coin collection to Cato's fund, and entertainers had offered to host the fundraiser event or host other events to support the money drive.

SARAH'S FIGHT FOR PERJETA - CAN YOU HELP?

If you can help Detective Sarah Cato by donating money to help her reach her goal of $130,000 for the life-lengthening drug Perjeta visit her Givealittle page above.

To help with her fundraising function by donating a venue, food, beverages, entertainment or silent auction items email [email protected] and your details will be passed on to the organisers.