A large-scale review of colonoscopy data from ambulatory surgery centers has found that 32% of individuals under age 50 have colorectal lesions. The findings support recent recommendations to lower the screening age for colorectal cancer from 50 to 45.

Almost one third of people between 45 and 49 years old who undergo colonoscopies have colorectal lesions, according to the largest study of its kind in people younger than 50 (Gastroenterology 2022 Jan 4 [Epub ahead of print]). The results support recommendations for earlier screening, particularly for those with a family history of the disease.

For reasons that aren't clear, colorectal cancer's incidence in people under 50 has been rising by about 2% per year since the 1990s. The surge has spurred the United States Preventive Services Task Force, the American Cancer Society, and the American College of Gastroenterology to recommend lowering the starting age for screening colonoscopies from 50 to 45 (JAMA 2021;325:1965–77; CA Cancer J Clin 2018;68:250–81; Am J Gastroenterol 2021;116:458–79). However, only a few studies have assessed the incidence of colorectal lesions in younger people, says Steven Itzkowitz, MD, of the Icahn School of Medicine at Mount Sinai in New York, NY. “We had limited information.”

To fill that gap, Itzkowitz and colleagues collected colonoscopy data from 123 ambulatory surgery centers in 29 states. They analyzed results from 562,559 colonoscopies, of which 225,932 were performed on people under 50. In this group, most people younger than 45 had the procedure after reporting symptoms such as abdominal pain; most people between 45 and 49 were undergoing screening.

The researchers determined that 32% of patients between ages 45 and 49 had lesions of some kind, including polyps, and 7.5% had advanced premalignant lesions likely to become cancerous. The rates were similar for people 50 to 54, 37.7% of whom had lesions of some kind and 9.48% of whom had advanced premalignant lesions. And the rates of colorectal cancer in the 40–44 and 45–49 age groups (0.53% and 0.58%, respectively) exceeded the rate in the over-50 group (0.32%).

Also of clinical importance, advanced premalignant lesions tended to occur about 5 years earlier in the patients with a family history of colorectal cancer than in patients with no family history.

Itzkowitz expected to see high rates of lesions but was surprised that the incidence in the 45–49 age group was so close to that in the 50–54 group. The data “justifies all the efforts to bring the screening age down to 45,” he says. Doctors need to start discussing the importance of colonoscopies with their younger patients, especially if there is a family history of colorectal cancer, so patients are prepared to begin screening at the appropriate age, he says.

“This is a very important contribution,” says Kimmie Ng, MD, of Dana-Farber Cancer Institute in Boston, MA, who wasn't connected to the study. “There was a dearth of real-world data” about how many average-risk, asymptomatic people under 50 had colorectal lesions. Still, she says, the sample was not representative—it included only patients screened at surgical ambulatory centers, and it included people who had diagnostic colonoscopies. But as more average-risk people between 45 and 49 undergo colonoscopies, “we can get better data” on the true prevalence.

Jordan Karlitz, MD, of Denver Health Medical Center and the University of Colorado School of Medicine in Aurora, who also wasn't connected to the study, agrees that it “supports reducing the screening age” to 45 in the general population. The relatively high rate of lesions in people under 45, 26.6%, raises the question of whether the starting age for colonoscopies should be even lower. But Karlitz says that “more information would be needed” before deciding whether to screen average-risk people under 45. –Mitch Leslie