Amid the throng of 90,000 runners tackling the Voltaren City2Surf this weekend, Robyn Smith will be carrying a deeply personal message.

The Canberra mother-of-three will run the 14-kilometre course from Sydney’s CBD to Bondi Beach topless.

Painted over her mastectomy scars will be the words, “Flat out for funding”.

Smith said the statement was not just about her own journey with inherited cancer; it was also aimed at raising awareness for the often-unexplored choice of “going flat” after a mastectomy.

The 46-year-old is collecting much-needed donations for the patient advocacy organisation where she works, Inherited Cancers Australia.

While she was feeling nervous about the run, Smith said she was inspired by UK flat advocate Louise Butcher, who has twice completed the London Marathon bare-chested to represent the thousands of women “living flat” without breasts.

Smith, 46, was pregnant with her second child back in 2012 when she discovered she had inherited a “ticking time bomb” – the BRCA2 gene mutation.

Women with the gene mutation have a 70 percent chance of developing breast cancer and a 17 percent risk of ovarian cancer.

“My mum died of ovarian cancer and my grandma died of breast cancer. My cousins had breast cancer, and my uncles had prostate cancer – we are all BRCA gene mutation carriers,” Smith said.

To reduce her risk of developing cancer, Smith chose to have a mastectomy, which was followed by a breast reconstruction.

In a story similar for many women, Smith said she was never really told much about the option of “going flat” before the surgery.

Instead, Smith was only provided with a “really nice glossy brochure about reconstruction, and nothing else.”

For Smith, it was almost assumed that getting breast implants was the option she would take.

She had breast implants put in and for 13 months, suffered from a cascade of debilitating symptoms she now attributes to breast implant illness.

“My hair was falling out. I had extreme fatigue, memory loss, brain fog, and one of my blood markers — my autoimmune, the ANA marker — went through the roof,” she said.

The symptoms became so severe that she had the implants removed after 13 months.

Almost immediately after “going flat”, her health began to improve dramatically.

“Within a few weeks, lots of my symptoms started to reside and everything went back to normal,” Smith said.

Her experience highlights a lack of education and choice for women undergoing mastectomies.

A further 18 per cent were told, but only after they asked about it.

“Flat is a valid option, just as valid as reconstruction,” Smith said, adding that thousands of Australians live happily and confidently without reconstructing their breasts.

For Smith, her run is also a tribute to her family, who weren’t given the same choices.

She feels “really fortunate to have had information that they didn’t have,” and while she is running for a serious cause, she expects her mum would had an amused reaction.

“Sometimes I think my mum must be up there just rolling her eyes and thinking, ‘What are you doing?'” she said.

The second message of her run is also a plea for help.

Smith and her colleagues at Inherited Cancers Australia are struggling to secure funding for the patient advocacy group, which has never received federal government support.

She hopes her bold action will grab the attention of corporate sponsors who might be willing to “support the little guy”.

The organisation provides crucial psychosocial support for families with inherited cancer risk, an issue that affects one in 400 Australians.

“I am doing this because I feel like we’ve exhausted a lot of other avenues,” she said.

“We’re doing something bold like this because we’re a small charity without sustainable funding.”

Smith says she has two messages she will be carrying to Bondi this Sunday.

“One of them is written on my chest, and the other is my chest.”