Rectal cancer deaths in Americans under 45 are rising up to three times faster than colon cancer deaths in the same age groups, according to researchers in New York who went through more than 20 years of CDC death records.
The findings are due to be presented at the Digestive Disease Week conference. The full results have not been published. Their announcement carried a blunt title, “Rectal cancer is striking earlier and killing faster,” and a blunt line: “Rectal cancer deaths among older millennials are accelerating, with growth in mortality far outpacing colon cancer.”
The team analysed US death records from 1999 to 2023 for adults aged 20 to 44, then broke the numbers down by age, sex, ethnicity and region. Machine learning projected the trends out to 2035. Rectal cancer deaths climbed two to three times faster than colon cancer deaths in every group studied. For adults aged 35 to 44, they were projected to keep rising all the way to 2035. Hispanic adults and people in Western states saw the steepest increases.
“Our study shows that rectal cancer is driving much of the increase in colorectal cancers, and it’s most likely to worsen over time if we don’t change what we are doing right now,” said Mythili Menon Pathiyil, the lead author and a gastroenterology fellow at SUNY Upstate Medical University.
No settled cause
Nobody has pinned down why. Growing evidence points to modern diets high in fat and low in fibre, which can slow digestion and leave waste sitting in the lower bowel longer. Processed meats and environmental pollutants such as pesticides may also play a part. The researchers could not say why Hispanic adults were hit hardest, though CDC data shows they are less likely than white Americans to have routine screening, and language barriers and limited access to care may delay diagnosis.
Rebecca Siegel of the American Cancer Society has described the wider pattern as a “birth cohort effect.” People born after the 1950s face higher risk, she said, which “tells us that there was some exposure, some risk factor that was introduced in the middle of the 20th century.” Known factors such as inactivity, obesity and alcohol do not fully explain the rise.
Late diagnoses
The American Cancer Society says colorectal cancer is now the leading cause of cancer death among Americans under 50. Diagnoses in that age group have risen by about 3 per cent a year over two decades. Three in four younger patients are diagnosed only after the disease has spread. Five-year survival is about 91 per cent when it is caught early, 74 per cent once it has spread nearby and 13 per cent once it reaches distant organs.
Becca Lynch, a Denver cyber security worker, was 29 when she was diagnosed with advanced colon cancer. She had “chalked it up to stress.” Her symptoms were pencil-thin stools, five or six trips a day and, eventually, thick dark blood. Siegel calls her story “very common.” Many people assume haemorrhoids, she said.
Doctors list other warning signs: iron deficiency, unexplained weight loss, bloating and pain after eating, and the feeling of not having fully emptied the bowels. Bright red blood can point to bleeding low in the bowel, while dark red or black stools suggest it is higher up. Anyone with these symptoms for three weeks or more should see a doctor, whatever their age.
Pathiyil said the results could push doctors toward earlier screening and wider use of sigmoidoscopy, which checks the rectum and lower colon. “It’s less about just changing guidelines overnight and more about changing how we think about it,” she said, “recognizing that colorectal cancer in young adults is no longer rare.”
Sources
- Colon cancer now leading cause of cancer deaths under 50 in US
- Rectal cancer deaths 'surging in millennials' – what you need to know
