In the United States, rectal cancer now makes up a larger share of all colorectal cancer cases than it did in the mid-2000s, primarily because more younger adults are being diagnosed with rectal cancer, while cancers in the upper part of the colon have become relatively less common.

We analyzed the available evidence and found that rectal cancer now makes up a larger share of all colorectal cancer cases in the U.S. than it did in the mid-2000s [1]. This shift appears to be driven by an increase in diagnoses among younger adults, while cancers in the upper colon have become relatively less common [1]. The evidence we’ve reviewed so far leans toward this pattern, though we do not have specific percentage numbers to show exactly how large the change is. What we’ve found suggests a reallocation in where these cancers are developing, not necessarily a rise in total colorectal cancer cases. The focus on younger adults points to possible changes in lifestyle, environment, or detection patterns, but we cannot say what’s causing this trend based on the evidence we’ve seen. We also cannot say whether this means more people are getting rectal cancer overall, or if it’s just a shift in where cancers are appearing within the colon and rectum. The evidence does not include data on total case numbers, age-specific rates, or long-term trends beyond the mid-2000s. For now, the clearest takeaway is that the profile of colorectal cancer in the U.S. is changing — more cases are showing up in the rectum, especially in people under 50. If you’re concerned about your risk, talk to your doctor about screening options, especially if you’re younger and have symptoms like changes in bowel habits, blood in stool, or unexplained weight loss.