Chris Burton was planning his wedding when he noticed he was bleeding after going to the bathroom.
He thought it was strange, but figured it was a one-off. Six weeks later, it happened again.
His GP referred him for a colonoscopy, and Mr Burton arranged to have the procedure after he and his wife returned from their short honeymoon.
The 39-year-old had advanced bowel cancer. The test results stunned him.
"That's probably similar to a lot of young people. Cancer's not at the forefront of what you think might be wrong with you," he says.
Australians aged in their 30s and 40s are experiencing unprecedented and in some cases world-leading rates of at least 10 different types of cancer — and scientists are desperate to understand why.
It's a question Mr Burton has struggled with since his diagnosis and one that's arrived at what should be a joyous time — the couple's about to have a baby, a little sister for their older daughter Isobel.
"That's the 3am thoughts that go through your head … have you done something to deserve it?" Mr Burton says.
The technical term for this phenomenon is early onset cancer and it is rising steeply.
Data provided to Four Corners by Cancer Australia, the federal government's cancer agency, paints a concerning picture for young people.
Between 2000 and 2024 — in 30 to 39-year-olds — early onset prostate cancer increased by 500 per cent, pancreatic cancer by 200 per cent, liver cancer by 150 per cent, uterine cancer by 138 per cent and kidney cancer by 85 per cent.
Some increases, such as prostate cancer, might be explained by changes in the way they are diagnosed — but most cannot.
"There are approximately 10 [cancers] that have this increase to varying percentages," says Cancer Australia's chief executive, Dorothy Keefe.
"Cancer has traditionally been a disease of aging, and bowel cancer, breast cancer, lung cancer, they all increase with age.
Australia isn't the only country seeing higher rates of cancer in young people either. Large amounts of data from US cancer registries show an even more pronounced trend.
Philip Rosenberg, a leading cancer bio-statistician who recently retired from the US National Cancer Institute, says there is a clear difference when comparing cancer rates between generation X and baby boomers.
"There were really very notable differences, for colon, rectum, thyroid, and pancreas, and as well prostate for men and ER (oestrogen receptor) positive breast cancer for women," Dr Rosenberg says.
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"In the youngest group of people that developed early onset colorectal cancer, we're seeing a much higher proportion that have a particular type of DNA damage pattern," he says.
That generational difference is so pronounced, he says he can tell whether a person is young or old from their tumour's DNA.
He says it suggests that there are factors or "exposures" that are contributing to an earlier diagnosis age for a group of colorectal cancers.
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Instead, most experts believe toxins or toxic influences in the world around us are interacting with genes to cause malignant changes.
In other words, you might unknowingly carry a gene that's only altered when you're exposed to a particular chemical, whereas someone else who doesn't have that version of the gene would be unaffected.
"Cancer is not a single disease, it is many different diseases," explains associate professor Gianluca Severi, a senior cancer epidemiologist based at the National Institute for Health and Medical Research (INSERM) in Paris.
"Within a disease that is called breast cancer, there are actually many diseases, but we know that there are different subtypes of breast cancer.