'Let's go outside and chat. I just love sunny days.” Natural enough considering the dark, gloomy and scary places that Leisa Renwick has visited recently.

'Melanoma is the cancer that gives cancer a bad name.”

Leisa Renwick with students.

That thought immediately focuses the mind. Because we were sitting in a sun-drenched leafy yard right outside Mount Maunganui College staffroom, blathering with the math teacher about kids, algebra, existentialism and the weather.

'When you think of cancer you think of someone getting progressively ill, they try some stuff, do radiation and chemotherapy, maybe it gets better; maybe it doesn't.”

Leisa is building to something. 'But with melanoma, you can be dead within weeks.” The good teacher pauses for effect. 'I went from work to being told I was going to die in a fortnight.”

Yet here she is – vivacious, insightful, funny and glowing with good health. She's back from a near death experience, back from being skeletal and back being normal again.

'Now I have to stop eating whatever I like and as much as I want because I am putting on too much weight.” She laughs because it's not life and death. 'No, it's a real problem – a problem we all have to deal with.”

We all know the name Leisa Renwick – she wrestled very publicly with the Government and Pharmac to get funding for a new drug for advanced melanoma. She ran a petition to press for funding, embarrassed a reluctant Health Minister Jonathon Coleman out of his office to chat on the issue. And at the end of the day she won.

That's Leisa the agitator, righter of wrong. 'We were just doing our part.” But there's also Leisa the wife and mother who's still battling – her own personal battle with an insidious disease. This is how a remarkable public profile evolved from a black, black day back in 2010, how a malignant mole transformed the math teacher into the poster person for a national cancer cause.

'I spotted it in the mirror and I decided I wasn't happy with it.” A mole had changed. 'I was having freak out so I went to the dermatologist the same day and demanded they remove it.” They did.

She's telling her story to a reporter who's just had a basal cell carcinoma excised from his shin. It wasn't life threatening and that's the difference between fair and unfair, cruel and kind. I dodged a bullet this time. But it struck Leisa Renwick.

'The dermatologist thought I was nuts.” But three weeks after Leisa's biopsy they came back to the observant, self-diagnosing math teacher and said: 'Actually you were right”.

They got it early, in plenty of time. There was a further and wider excision and annual skin checks. 'But otherwise you will be fine,” they said. Of course there can be no guarantees with cancer. And there wasn't.

'In May last year I got a little bit queasy, a little bit crook.” There were visits to the doctor, days off work and eventually hospital with a bloated abdomen. A week later another bullet.

'Stage four metastatic melanoma. Sorry nothing we can do, we will sort out pain relief, go home to your family.” Yes, just like that. But she didn't believe them, she was in complete denial. And she got angry with doctors who she says: 'Wrote me off”.

'Hospital doctors travel in packs. One important one up front and the rest taking notes. So before they came into my room I would ask if they were the ones coming to save me or the group who'd given up. ‘Because if you are the ones who've given up, you can get out now'.”

She enjoyed that. Leisa – sick, dying but oodles of attitude, a fighter.

'I was too sick to be useful but my husband Wayne stepped up, researched and turned all his attention to the problem.” A hospital doctor kindly referred them to a private cancer clinic.

It's ironic that had she been given the flash new immunotherapy drug called pembrolizumab, better known by its trade name Keytruda – the one she'd been championing, the one she helped get funded – it would not have saved her. She was too sick.

However, there was another new drug, debrafenib. If a biopsy had a BRAF gene mutation, and there was a 50/50 chance, then a cancer patient could go on debrafenib. In layman terms it starves the cancer of the protein it needs to thrive, a kind of cancer growth blocker.

'But they looked at me and said there's probably no point. ‘She is not going to make it long enough for the test results to come back'.” As soon as there's hope, it's dashed.

Again Wayne stepped up again. 'Do the test,” he said. 'And I will pay.” Family and friends also stepped up, staying with Leisa 24 hours a day, feeding her a spoonful of food every hour, just enough to keep her alive until the tests came back.

It was positive – she had the gene mutation. Wayne wrote out a check for $12,000 for the first prescription although the cheque was never cashed. Leisa got the drugs on a compassionate programme with the drug company.

One minute she had been directed to a hospice – next minute she was being handed the 'inhibitor” – new hope in a bottle. A drug that oncologists have described as 'like nothing else we have ever known”.

'Within days of starting the drug – and I am not exaggerating when I tell you – within a couple of days of taking those pills, I was standing up and walking around. Okay, I was still weak and tired and I had lost huge amounts of weight, but I was standing and walking,” says Leisa.

'And only days before my body had been shutdown – I had that sallow look, the look of death. Then suddenly the cancer was arrested.”

We both stop and ponder what's happened here. To appreciate her good fortune you have to understand the gloomy place she came from.

Earlier they'd sent Leisa home in an ambulance one Friday and told her she would be dead by Monday. 'Gather your family.” Then a short time later they're telling Leisa she's in complete remission. 'The cancer's gone, we cannot see anything in there anymore; it's all gone.”

'It's simple,” says Leisa. 'I can put it down to the drug that I am still here.”

And it's if Mount Maunganui College is right this minute celebrating her remarkable fortune. There's music ringing out across the campus, students are laughing and chattering and milling, the place is alive with young, new hope.

But also tinged with realism. 'I was told this straight out. When the gene therapy drugs stop working, they stop working as fast as they worked. And cancer always develops a resistance. 'It always works its way around a drug.”

And just when my hopes for Leisa were building, just when I was wanting to believe she was bullet-proof.

'I was taken off the gene drug when it was at its optimum. I had to move on before they stopped working.” Now she's on pembrolizumab or Keytruda at $8500 every three weeks. Life threatening illnesses are draining emotionally and financially. 'But it's kept me alive.”

Eventually she will transfer back into public system – and eventually she will get the same drug by another name and it will be funded by Pharmac. Eventually. And she will become a beneficiary of her own battle for what she believed was right and fair.

She can deserve to feel a little smug about that. 'But it will come back. It will come back.” She's very matter of fact and hugely inspiring and brave.

In the meantime all is very good – she's worrying a problem she has some control over – her weight. She's soaking up a stunning autumnal day and about to teach teenagers how to add the letters A and B.

'A and B aren't letters,” says the math teacher. 'They're numbers.”

And there's her existential crisis to deal with now.

'I have been too busy. Because I jumped straight from dying to getting well, to organising a petition, to walking into Parliament and working.”

Perhaps it's a good time to stop and ponder life, all those wonderful things that make us who we are, what we want to do and where we want to go. That should focus the mind too and fill a couple of hours in a sunny leafy school courtyard.