Sarah became lactose intolerant at 22. She knew it was a deadly sign.

When Sarah Graham turned 22, she became lactose intolerant "suddenly, out of the blue." It was the first sign that something was wrong, but it would take seven years for the Victorian interior designer to get answers.

To be diagnosed with Stage 3 bowel cancer.

"Like a flick of a switch my bowels weren't right," Sarah told Mamamia, adding she would have the urge to go to the bathroom after eating anything with dairy.

"That progressively stayed with me until I was 26."

The facts on bowel cancer. Post continues after video.

At 26, Sarah was diagnosed with endometriosis and lesions were found on her bowel. Doctors removed these, and by avoiding dairy, her symptoms improved for a few years.

But things would take a turn in 2024, when Sarah was on the cusp of turning 29.

Around January, Sarah began exhibiting a concerning host of symptoms. This time, she knew something was seriously wrong.

"There was extreme pain with my bowel movements," she said. "To the point [where] I would be in tears trying to go to the bathroom. It was just the most painful, most excruciating experience.

"I had put on 20 kilos of weight. I was retaining a lot of fluid.

"There was just something inherently with my gut that wasn't right."

Sarah went to her GP, hoping to get answers. She was left with more questions.

"They did all sorts of diagnostic testing," Sarah said, adding that her doctor's hypotheses ranged from hormonal changes to a slowing metabolism and circulation issues.

Of all the symptoms she presented with, doctors were most concerned with Sarah's fluid retention.

"They weren't concerned with the painful bowel movements, they weren't concerned with the weight gain," she said.

Sarah said her symptoms were continually dismissed. Image: Supplied.

Disheartened, Sarah walked away and hired a nutritionist. She started counting calories and went on a diet. Still, her weight didn't budge.

Months passed.

Then in July, she noticed blood in her stool.

Again, she went to her doctor, who initially dismissed the symptoms as haemorrhoids, or a fissure.

But this time, Sarah pressed for tests.

"Basically, my GP said, 'You're way too young for this to be anything serious… we'll do a stool test'," she recalled.

That test came back inconclusive, so Sarah was referred for a colonoscopy.

For two weeks, she didn't hear anything. When she followed up, she was told that she had been "triaged as non-urgent". The earliest appointment they had for her was late November, so she took what was available.

Sick of juggling work, fear and fatigue, Sarah had a conversation with her parents, who urged her to book an appointment with another GP for a second opinion.

"I explained my symptoms again to her, and said, 'Look, [the blood] is happening almost every time I go to the bathroom now. I'm getting really scared to go to the bathroom," Sarah said.

The GP called a gastroenterologist while Sarah was still at the appointment. On hearing Sarah's symptoms, the specialist offered to stay back after hours to see her that night.

"In that first consultation, they said, 'You're looking at something like Crohn's or Irritable Bowel Syndrome (IBS). You are way too young for bowel cancer. We've never seen it in someone your age.'"

A week later, the results from her colonoscopy came back.

'It was like all the items in the room disappeared.'

Eleven days after Sarah's 29th birthday, she woke up groggy from anesthetic after the colonoscopy.

While the procedure itself had been "traumatic", Sarah was more concerned with the series of strange interactions taking place as she came to.

She remembers talking to a young nurse when a more senior nurse stuck her head inside the curtain.

"I was of course still a bit out of it, but was lucid enough, and she said, 'Look, don't tell her anything,' in front of me," Sarah said. "It was getting to 6pm at night and I was the only one in the recovery room and, for some reason, none of the nurses were stopping to talk to me. They were all staring at a distance.

"My surgeon walked past me a couple of times and didn't make eye contact. Then all of a sudden, my mum came through the double doors. I thought, 'That was weird', [because] everyone that was discharged that I saw walked out to their family members."

As Sarah's mum sat down, her surgeon came over at last.

Then came the words that would forever change Sarah's life.

Sarah first noticed symptoms at the age of 22. She was diagnosed with Stage 3 Bowel cancer eleven days after her 29th birthday.

"He said, 'Look, we've found a mass we couldn't transverse. It's likely malignant. We've referred you for an urgent CT scan tomorrow. We've already made that appointment for you, but we need to move quickly on this.'"

Sarah said that "it was like all the items in the room disappeared".

But she wasn't shocked.

"I knew something was wrong. I never expected this. I felt let down, I think," she said.

"The first thing I said to him was, 'Am I going to die?' to which he said, 'Look, I hope not'. To this day, I still feel so let down by the medical system.

"I know my body, and I knew what I was living with and no one would listen."

'One of the fastest-growing cancer epidemics of our time'.

In Australia, 15,542 new colorectal cancers were diagnosed last year, according to Bowel Cancer Australia.

Sarah was just one of these.

The number of bowel cancer cases is rising in young patients globally. Experts are so concerned that it's being called "one of the fastest-growing cancer epidemics of our time".

New research from the University of Melbourne found Australia now leads the world for bowel cancer rates in people under 50 years of age. An Australian born in 1990 is now up to three times more likely to develop the disease compared to someone born in the 1950s.

But despite the surge in cases, many younger patients, like Sarah, are struggling to get a diagnosis.

Sarah believes one of the reasons she was dismissed as a potential case, other than her age, was the fact she exhibited weight gain — bowel cancer is typically associated with weight loss.

Sarah Graham said she feels 'let down' by the medical system. Image: Supplied.

"All you have to do is put your ear to the ground, or type it into Google and you can see this is an epidemic now," Sarah said.

"The amount of people this is happening to, and the amount of people where it is being caught too late. I think to myself, had I listened to that original doctor who booked me in 'non-urgent' who knows what would've happened.

"I was living with Stage 3 cancer and I had no idea."

Researchers don't know what's behind the increase in cases, but recent research suggests a toxin produced by certain strains of the bacterium, Escherichia coli, in early childhood could be a culprit.

Microplastics have also been floated as a possible cause, and lifestyle factors such as obesity, physical inactivity, excess alcohol consumption and smoking are known to raise risk.

'It still doesn't feel real sometimes'.

Once Sarah did finally get a diagnosis, she's thankful the response was quick. Within two weeks, the mass was removed, and she commenced treatment, completing eight rounds of chemotherapy over the following six months.

"My prognosis at this stage is good," she said, explaining she's now in a five-year surveillance period. "They've put me in a low risk of recurrence category but, of course, there is no life free of the burden of cancer, unfortunately.

"My normal looks very different, and it will for the next five years at least."

Sarah has neuropathy — nerve damage — in her hands and feet as a result of chemo, and has had to overhaul her entire diet because part of her colon had to be removed.

She is now telling her story so that other people know how to advocate for themselves when they suspect something isn't right.

"It still doesn't feel real sometimes, but I know that as long as I'm willing to tell my story, it's important to [do so], because I'm hearing people are being let down.

"It sounds really clichéd, but I would say [to people], 'Trust your gut'.

"The best piece of advice I was given is that if your GP says no to something you request, ask them to write that down. You will quickly realise that if they don't want to put their name to denying you something, and something happens later, they don't want to be liable for it.

"If anything is out of the ordinary, you need to get it checked."

Image: Supplied.