Colorectal cancer is now the leading cause of cancer death for Americans under age 50, highlighting that colorectal cancer is an increasing threat not only to older adults, but also to younger men and women.

“Now we’re starting to see more people developing colon cancer in the 20-, 30-, and 40-year-old age group. Early in my career, no one was getting colorectal cancer at that age,” says John Marshall, MD, of Georgetown University’s Lombardi Comprehensive Cancer Center in Washington, who has been a cancer doctor for more than 30 years.

Marshall added: “Frankly, this trend is shocking to all of us.” Mr. Marshall is also a medical consultant for the Colorectal Cancer Alliance, the largest colorectal cancer nonprofit organization in the United States.

Here’s what you need to know about colorectal cancer at any age and how to protect yourself.