Overall colon cancer rates in the United States have declined steadily over the last 30 years. But rates of colon cancer in young adults have risen dramatically during this period for unknown reasons.

Colon or rectal cancer that develops in people under age 50 is often referred to as early-onset colorectal cancer. Rates of early-onset colorectal cancer in the United States have nearly doubled since the early 1990s and similar trends have…