Education More than 1.9 million people around the world were diagnosed with colorectal cancer in 2020, which affects the large intestine (colon) and the rectum. While the average age for colorectal cancer diagnosis is about 66 years old, recent studies show there is a marked increase in the amount of younger adults being diagnosed. Research presented in May 2024 reported that colon cancer rates increased by 71% in adults ages 30 to 34 and 58% in adults ages 35 to 39 between 1999 and 2020.