Colorectal cancer is falling among Americans 65 and older, but it is rising sharply in people under 50, according to recent research that points to one of the clearest age splits in modern cancer trends. The shift matters now because it is changing who shows up in clinics with the disease and how likely they are to survive it.

In 2026, about 158,850 new cases of colorectal cancer were diagnosed in the United States, and more than 86,000 of them were in people over 65. That older group has seen cases decline by 2.5% a year since 2013, while people ages 50 to 64 have seen a 0.4% increase per year and those ages 20 to 49 have seen a 3% annual rise. The pattern is broad, reaching every racial and ethnic group.

Doctors say the drop in older adults tracks with screening, especially routine colonoscopies that start at 45 for people at typical risk. During those exams, doctors can remove precancerous polyps before they turn into cancer. The rise in younger adults is a different story. Researchers believe some change that began after the 1960s is helping drive the increase, most likely a shift in environment or lifestyle, though no one has pinned down the exact factor.

That uncertainty is part of what makes the trend so hard to reverse. Younger people also tend to wait longer between the first symptoms and diagnosis, and most colorectal cancers in that age group are found at a late stage, when treatment is more difficult. Dr. Geoffrey Buckle said many of his patients are his peers, people with young children, pregnant partners or careers just getting started, and that they are hit with diagnoses that are obviously terrifying.

The research suggests the driver may be affecting cancers of the rectum and the lowest part of the colon more than other areas, which could help explain why the younger-patient surge has been so persistent. But that same finding leaves health officials with a gap: screening is catching more disease in older adults, while younger patients are still arriving too late. For now, the answer to why the trends are moving in opposite directions is not that doctors are seeing more of the disease overall, but that colorectal cancer is increasingly becoming a disease of the young even as it recedes in the old.