Cassandra Thorburn apologises as she pulls a tissue from her bag and puts it gently against her nose. That the hairs in your nostrils fall out, along with those on your head, was one of the many things she didn’t know before being diagnosed with a rare form of breast cancer at the start of this year.

No hairs in your nostrils means no barrier to the many micro elements flying around your vicinity. “Your nose runs because there’s nothing there,” Thorburn tells me matter-of-factly. “So if I’m in a new space, all the dust goes straight into my body.”

Not that she’s in a bad way on this late winter’s day. To the contrary, after being in treatment of one form or another for most of the year, the 55-year-old was recently declared cancer free. She’s still having radiation and immunotherapy, to mop up any stray cancer cells that might have escaped. But the gruelling days of chemotherapy are done, ditto an operation to remove 11 lymph nodes. Two subsequent hospitalisations due to immunity issues are also behind her.

Pleasingly, her hair has started to grow back. She jokes about a recent video call she had with her boss, who was diagnosed with breast cancer seven weeks before her. “We were laughing about the fact that the two of us no longer looked like we’d been through chemo, we now looked like we were from [the TV show] Prison Break.”

After a long dark winter, it seems, spring is in the air. It feels like that here, too, at L’Heritage, a delightful French bistro deep in the Clifton Gardens Reserve on Sydney’s North Shore. Chowder Bay sparkles out the window as we peruse the menu, both settling on the fish, adding sides of honey-glazed Dutch carrots with pistachio and a Mesclun salad to share.

Thorburn hasn’t been out to lunch much this year, for obvious reasons, and while she still can’t drink alcohol, and cannot yet stomach chicken or spicy foods, she’s palpably excited to be here. For the food, yes, but also for the mission. “I made a promise to myself when I was diagnosed that I would raise awareness about occult triple negative breast cancer, and I’m honouring that.”

We’re in Thorburn’s Mosman-Cremorne-Neutral Bay ’hood, and she chose this restaurant because French food became a treat night out with her kids after her former husband, the breakfast TV host-turned-podcaster Karl Stefanovic, left their 21-year marriage back in 2016. (He subsequently remarried and had a fourth child.) “It became a thing when we became just a family of our own. There was a local French restaurant, nothing fancy like this, but we’d go there for birthdays.”

Even though her marriage ended a decade ago, Thorburn has been most known in the public eye as Stefanovic’s ex – or in her words, the “bitter ex-wife”. Sure, she went on Dancing with the Stars and fronted a podcast on divorce, and made some spiky comments, including about how much she’d contributed to his career as the primary carer of their three children. But she’s also done a raft of quieter things in the post-Karl years, including working in marketing for a homeless shelter, caring for the aged during the COVID-19 pandemic, and training as a dental nurse. Decidedly un-spiky things. These days, she works for an NGO aged care provider that sends profits back to army veterans. “The media wanted me to be a bitter ex-wife because there’s a name for it, because that’s what they call every ex-wife,” she says. “What’s the term for the man? They never use one.”

That’s all in her “rearview mirror”, Thorburn says. A former journalist and daughter of one, she understands how it works, but not surprisingly, has lost a lot of faith in the fourth estate. Which is where social media, so often the cause of societal ills, has proved a boon, allowing her to rewrite that public narrative with her own unfiltered words, such that “cancer campaigner” is now a better descriptor of her.

“I have an inherent distrust of the media because they decided who they wanted me to be, not who I am,” she says. “They weren’t interested in who I was while I was married, but once I got divorced, they certainly decided who I should be and how that was going to play out. So I felt this time, when I was diagnosed, I’m not going through that again. I can tell this story myself.”

To that end, over the course of this year she’s been speaking plainly to her 14,100 Instagram followers about what it’s like to have cancer, and the various rabbit holes she’s gone down searching for greater information and understanding. “When I was diagnosed I didn’t think ‘why me’, I thought ‘why it’s me’,” she says as we tuck into a gruyere souffle L’Heritage has offered on the house. “I have a small platform on social media, and I thought, if I can educate one person, or five people, it’s like Chinese whispers, right?

“They’ll tell five people, and they’ll tell five people, and they’ll tell five people, and more women will talk about it, and that’s what I wanted to happen.”

The occult form of breast cancer accounts for less than 2 per cent of breast cancer diagnoses in Australia, unusual enough that it doesn’t rate a mention on the Rare Cancers Australia website. (Thorburn hopes to change that.) Hidden in the lymph nodes, it’s difficult to detect as there’s no lump, no primary – and lumps are the one thing us women have been taught to check for. In her case, she only had a mammogram because the letter from government arrived offering a free one. “The mammogram showed nothing in my breast, but it showed a grey area on the side which, thankfully, some amazing radiologist looked at and went, hmm, we might call her back,” Thorburn says. Various tests later, she was diagnosed. Within nine days, she’d started chemo.

She was shocked to read that only just over half of the Australian women aged between 50 and 75 who are sent the free mammogram letter take it up – especially given a mammogram is the only way a cancer like hers would be detected. She thinks she might have had a bit of a sore underarm ahead of her diagnosis, that she put down to the martial arts training she was really into, but says it’s equally possible she’s retrospectively imagined this to make sense of it all. “I was doing Muay Thai, I was so fit, the fittest I’d been in so long,” she says. “I was through menopause, I was really feeling pretty great. I guess that’s why they call it a silent killer.”

The rawness of her Instagram posts are what freights them with power. There’s no hair and make-up, no attempt to disguise how bloody awful a lot of it is – the exhaustion she’s felt from the “red devil” chemo treatment, the two steps forward, one step back, the steroid bloating, the thrill at being finally able to go for a short walk again. The value of services like the free head shaves Toni&Guy offer those embarking on chemo, and the penny drop when she realised “cancer ghosting”, or the disappearance of some friends from your life post-diagnosis, is a thing.

“Some people either don’t know what to say or, just too much time passes in their head,” she says of what she researched about ghosting. “If you are diagnosed with cancer, I can guarantee, you have zero expectation of anyone else. You don’t start judging your friends or colleagues, or anyone you have known in your past, and thinking, ‘why don’t they reach out to me’? That’s not what you’re thinking. What you are thinking, though, is you don’t expect people to leave.”

Some followers took the ghosting post to mean she was on her own. “I had to reassure people, I’m not alone,” she says as our fish and salads arrive. “My mum, bless her, came and stayed with me for more than three months.” What should people do, I ask, if someone in their orbit is diagnosed with cancer. “Just stay in touch,” she says. “Check in. It’s never too long.”

Thorburn made a close “chemo buddy” during treatment, one of the silver linings from the whole experience. “Being able to say to someone, I feel really shit, this is what’s going on, and you know they actually know because they’re going through it as well. It makes a huge difference,” she says. “I remember reading something in an online forum where someone said, breast cancer is the worst club to be in, with the best members. I love that.”

I can’t help but wonder what her ex-husband had to say about her cancer diagnosis, whether it brought them closer again. She didn’t hear from him, she tells me evenly. I express surprise. Did that shock her? “No, I know who he is. It’s others that don’t.” [This masthead contacted Stefanovic for comment.]

While we’re on the topic, which I promise will be brief, I wonder what she makes of his seeming lurch to the right since leaving Nine, the publisher of this masthead, and becoming a podcaster. Was he always that way inclined or is it a new persona? “He’s always been into clickbait,” is all she’ll say. The fact that comedians like Henry Bretz are gaining traction by impersonating her ex must amuse her though, I venture. She smiles, leaves the space silent – is not naive enough to answer.

Thorburn was a broadcast journalist too, but gave it up after having kids. She seems to have moved deliberately away from that glamorous world, I say. She counters that maybe that world “didn’t sit well with me” from the start, “maybe that’s why it didn’t work out”.

I assume that Thorburn, like most women, won’t want dessert, so I tell the waiter we won’t have any. I’m a tad embarrassed when she corrects me – she’s hardly tasted sugar this year and would very much like some. She settles on the fondant au chocolat and I join her with a tarte tatin. I ask what’s on her list now that she’s coming out the other side. She wants to continue her campaigning about occult triple negative breast cancer. She’s already spoken at some fundraising lunches and on September 20 will walk with her son River and his girlfriend in Carmen’s Fun Run Sydney, raising funds for Breast Cancer Network of Australia.

She’d like to visit her daughter Willow in London, which she was going to do this year before cancer so rudely intervened, and wants to get back to full-time work. She’s not on any dating apps and says it’s not a priority, she’s always preferred meeting people the old-fashioned way, anyway. Other than that, she just wants to enjoy life. She’s not a bucket-list kind of person. “I’m not one of those people who has to plan everything in my life. I just want to be present for the rest of this journey.”

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