Karen Maddison joins Luke Alexander's The Big Three Trek from Newcastle to Sydney after breast cancer battle

"I just thought, oh my God, this is definitely not something I wanted to hear," the 48-year-old said.

"I thought, 'how am I going to tell my children, especially my daughter?' Being a woman, you know, I thought of her. We're pretty close, and I thought, now I have to tell her and explain this to her."

The diagnosis also sent her mind towards some of the more negative possible scenarios.

"I was thinking, I'm going to have a mastectomy and have to go through chemo and I sort of was thinking of the worst," she said.

"Being in healthcare - I worked at the large residential center at Stockton for 28 years - sometimes, that can be a good thing but sometimes it can be a bad thing. Like you know too much. And Dr Google definitely doesn't help either."

The worry was slightly eased when Ms Maddison was later told the cancer hadn't spread. In June, she underwent lumpectomy surgery, before starting chemotherapy a few weeks later and then radiation, which she has will finish today.

As this was all happening to the Caves Beach mum, fellow Hunter local Luke Alexander was on a journey of another kind - a 150 kilometre walking journey from Sydney to Newcastle over three days in June, to raise money for the Mark Hughes Foundation.

A group of 26 dedicated participants completed the Big Three Trek, which was organised by Mr Alexander and his mates Nathan Hill and Ethan Coker. It raised more than $100,000 for brain cancer research.

One of the trek participants was reality TV personality Ryan Gallagher, whose mum has battled breast cancer.

He asked Mr Alexander afterwards if they'd consider doing the walk again, this time in aid of breast cancer.

"I said yes straight away," Mr Alexander said.

The three and a bit day trek will support the McGrath Foundation and provide funding for breast care nurses, who provide physical, psychological and emotional support for patients. The walk will start on January 2 at McDonald Jones Stadium and finish at the Sydney Cricket Ground, where Glenn McGrath will greet the group on the first day of the Pink Test.

Ms Maddison began her own fundraising after being diagnosed to give her something positive to focus on.

She then saw The Big Three Trek pop up on Facebook.

"I thought, oh, that's something I'd like to be involved in," Ms Maddison said. "I thought it was fabulous. It's such a good cause to help people and provide support, and for their families as well."

Ms Maddison has signed up to do the first day of the walk with her daughter, which is about 50 kilometres - an impressive feat for anyone, let alone someone who has just finished cancer treatment. But Ms Maddison says that's part of what's driving her.

"I'll definitely read some of the stories of other people that have been through the breast care journey and breast cancer. I feel that will inspire me to do it for them," she said.

Mr Alexander said it was amazing to see Ms Maddison volunteer to participate.

"It's pretty inspiring," he said.

Some recognisable names have also signed up to the walk, including former NRL players Brett Finch, Billy Peden and Akuila Uate, local reality TV personality Elly Miles and former local W League star Rhali Dobson.

The final kilometre will also involve an impressive contingent of celebrities, including TV stars, athletes and even The Wiggles.

Mr Alexander said during the last trek, a lot of the participants said they had been impacted by breast cancer in some way or another.

"Unfortunately so many people are affected by it," he said. "Most people would know someone who's had it."

The group has already raised more than $56,000, which they hope to almost double before they complete the walk.

To donate, visit fundraise.mcgrathfoundation.com.au/event/big-three-trek/home