Nathan Borg was still groggy from anaesthesia when his doctor told him he had bowel cancer.
The 29-year-old was three months shy of his wedding date. His fiancée, Samantha, sat next to him, sobbing.
“I had just bought a house, I had a mortgage, I was getting married,” Borg said. He assumed his colonoscopy would confirm the blood in his stool was due to haemorrhoids.
“I never thought for a second that it was cancer.”
A growing number of young Australians are being diagnosed with bowel cancer for reasons that are not well understood. The incidence in people in their 30s is up by 137 per cent since 2000.
But a subset of patients – about one in six – seem to have tumours with a genomic quirk that makes them “exquisitely sensitive” to immunotherapies, as one global leader in precision oncology put it.
An analysis of a cancer patient cohort whose tumours were considered incurable or advanced found that a third of bowel cancer patients were under 50 years of age.
Almost 14 per cent of bowel cancer patients were under 40, the analysis of Omico’s database found. The analysis is an initiative that facilitates genomic profiling for cancer patients with poor prognoses and matches them with next-generation therapies or clinical trials.
Two per cent were aged under 30 (about 60 people). Fourteen patients were diagnosed with bowel cancer before they turned 25.
“It is absolutely devastating to receive a diagnosis so young,” said Omico founder and chief scientist David Thomas.
Bowel cancer in young Australians is still very uncommon (the number of cases in 30- to 39-year-olds rose from a low base of 184 in the year 2000 to an estimated 772 in 2025), and survival rates are rising.
Most bowel cancers, which is also called colorectal cancer, are still among the over 50s (at which age Australians automatically receive a bowel cancer screening kit, which can be requested from 45).
However, the cancer could no longer be considered one of older people, Thomas said.
“We need to understand why the incidence of early onset colorectal cancer is rising. Is it environmental or microplastics? Is it diet? It isn’t genetics alone, but there may be a genetic component,” he said.
Thomas said that up to 15 per cent of colorectal cancers had a genomic signature called microsatellite instability (MSI), which occurs when DNA mismatch repair proteins cannot fix errors in short DNA sequences. Most occur spontaneously, rather than being inherited.
“These tumours are exquisitely sensitive to immunotherapies,” Thomas said.
Borg’s cancer was one of them. He didn’t know that when he began a deeply confronting sequence of radiation and chemotherapy to shrink his six-centimetre-long tumour, and surgery to remove 30 centimetres of his bowel. He also lived with a stoma for six months.
“I lost my hair twice, and I had all the other fun symptoms of chemo,” he said.
He could not afford to take time off work as a project manager for a commercial fit-out company.
But when cancer spots were found in his liver, his oncologist found the key to his survival.
Fittingly, Dr Siobhan O’Neill was sitting in a session at the Australian Gastro-Intestinal Tumours conference, and she opened up Borg’s Omico test results. He was “MSI-High”.
“I jumped in my seat. I thought: ‘Oh, my God, this is amazing news. He can have immunotherapy’,” O’Neill said.
MSI testing is a routine part of the pathology process for newly diagnosed bowel cancer, which picks up most MSI-H tumours’ status via a surrogate marker.
Borg’s specific gene mutation meant there was no way to detect his tumour’s MSI signature without genomic testing.
Further genomic testing found Borg had Lynch syndrome, an inherited genetic condition that accounts for up to 15 per cent of MSI-High colorectal cancers.
Borg had no trouble tolerating the PBS-funded immunotherapy drug pembrolizumab for his two-year course. He has been cancer-free since January.
“It was a game-changer,” Borg said. He and Samantha are expecting their first child in August.
“I always knew I’d beat it in the end.”
Quick facts: bowel cancer patients in Omico’s cohort
- Bowel cancer accounted for 11.5 per cent of 3024 people who have been referred for comprehensive genomic profiling and treatment matching.
- 34 per cent of the bowel cancer participants in Omico’s programs are under 50, compared with 23.5 per cent across all other cancers
- Almost 80 per cent of bowel cancer patients got a matched treatment recommendation
- One in five enrolled in a clinical trial or accessed a treatment they were matched to after undergoing genomic profiling
Cancer Australia chief executive Professor Dorothy Keefe said lowering the bowel cancer screening age would cost an enormous amount of money that could be better spent. It could also cause harm to people who don’t have cancer; and clog up waiting lists for colonoscopies, which would delay cancer diagnoses
Keefe urged young people to see their GP if they noticed blood in their stools, changes in bowel habits, or any changes in their health that don’t resolve, including pain, vomiting, unexplained weight loss, fatigue or low haemoglobin.
Cancer Australia has commissioned an evidence review of early onset cancer risk factors, while updated evidence-based guidelines reflect how young people present with cancer and what investigations and referrals to pursue.
“We, as a medical profession, need to reframe our thinking about cancer presentation in young people as this becomes more common,” Keefe said.
Cancer Australia and the National Health and Medical Research Council announced on Monday $15 million to help fund seven research projects on early onset cancer risk factors, tests and treatments. Three projects will focus on colorectal cancer.
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