Colorectal cancer rates rise from 3 to 13 per million

Colorectal cancer is largely a disease of older adults. More than half of cases are diagnosed in people over 65, and only 16% occur in those 49 or younger. In the United States, only a few hundred cases a year are diagnosed in people under 21, yet the number among the very young is rising. The decline in older-adult diagnoses likely reflects routine colonoscopies that remove precancerous polyps. Researchers suspect environmental factors such as ultraprocessed foods and sedentary lifestyles may be behind the rise in youth.

The new study of 84 patients diagnosed between 2012 and 2023 found a median diagnosis age of 16 and a median symptom duration of 12 weeks. Only about 20% had a close relative with colorectal cancer, suggesting that hereditary factors do not explain many of these cases. Eighty percent of the patients were at Stage III or Stage IV when diagnosed, compared with 60% of patients of all ages. One-third carried cellular markers of particularly aggressive cancer.

Experts are looking to the gut microbiome for clues. Disruptions in the community of gut bacteria may spark inflammation, which in turn may trigger DNA mutations. Factors such as processed food, antibiotic exposure in childhood, stress and reduced exercise may contribute to the increased risk. One specific variant of the common gut bacterium Escherichia coli, which carries a toxin-producing genetic segment, is strongly linked to colorectal cancer. It does not explain all cases, however.

Common symptoms reported by the study's patients include back and abdominal pain (75%), changes in bowel movements (45%), unexplained weight loss (43%) and rectal bleeding (38%). These symptoms are classic for colorectal cancer, but they can be mistaken for more common gastrointestinal problems in children. Pain or stomach upset that does not ease or that worsens over time needs a checkup. Weight loss and blood in the stool are very unusual in children and deserve extra attention.

CDC data show a sharp rise in diagnosis rates among younger age groups. In 1999 the rate for children aged 10 to 14 was 1 in a million. By 2020 it had risen to 6 in a million. For teens aged 15 to 19, the rate grew from 3 to 13 in a million over the same period. The study's data are not nationally representative.