SAN ANTONIO – The American Cancer Society’s 2018 qualified recommendation to lower the starting age for colorectal cancer screening from 50 to 45 years in average-risk individuals has picked up new support from a New Hampshire Colonoscopy Registry analysis.
Data from the population-based statewide colonoscopy registry demonstrated that the prevalence of both advanced adenomas and clinically significant serrated polyps was closely similar for average-risk New Hampshirites age 45-49 years and for those age 50-54, Lynn F. Butterly, MD, reported at the annual meeting of the American College of Gastroenterology.
“The clinical implication is that our data support the recommendation to begin average-risk colorectal cancer screening at age 45,” declared Dr. Butterly, a gastroenterologist at Dartmouth-Hitchcock Medical Center in Lebanon, N.H.
The American Cancer Society recommendation to lower the initial screening age was designed to address a disturbing national trend: the climbing incidence of colorectal cancer in young adults. Indeed, the incidence increased by 55% among 20- to 49-year-olds during 1995-2016, even while falling by 38% in individuals age 50 years and older. The 2018 recommendation was billed as “qualified” because it was based upon predictive modeling and National Cancer Institute Surveillance, Epidemiology, and End Results data which have been criticized as subject to potential bias. Several studies conducted in Korea and other Asian countries have reported a lower colorectal cancer risk in the younger adult population than in those age 50 or older, but questions have been raised about the applicability of such data to the U.S. population.
For Dr. Butterly and coinvestigators, the research imperative was clear: “We need to generate U.S. outcomes data for average-risk individuals age 45-49, versus those over age 50, for whom colorectal cancer screening is already strongly recommended.”
Toward that end, the investigators turned to the New Hampshire Colonoscopy Registry, which contains detailed data on 200,000 colonoscopies, with some 400 variables recorded per patient. To zero in on an average-risk population below age 50, they restricted the analysis to patients undergoing their first colonoscopy for evaluation of low-risk conditions including abdominal pain or constipation while excluding those with GI bleeding, iron-deficiency anemia, abnormal imaging, or a family history of colorectal cancer.
The final study population included 42,600 New Hampshire residents who underwent their first colonoscopy. The key outcomes were the prevalence of advanced adenomas, defined as adenomas more than 1 cm in size, or with high-grade dysplasia or villous elements, and the prevalence of clinically significant serrated polyps larger than 1 cm, or larger than 5 mm if proximally located, as well as traditional serrated adenomas and those with sessile features.
The prevalence of advanced adenomas in 1,870 average-risk patients aged 45-49 years was 3.7% and nearly identical at 3.6% in 22,160 individuals undergoing screening colonoscopy at age 50-54. The rate of clinically significant serrated polyps was 5.9% in the 45- to 49-year-olds, closely similar to the 6.1% rate in patients age 50-54.
Of note, the prevalence of advanced adenomas was just 1.1% in individuals younger than age 40 years, jumping to 3.0% among 40- to 44-year-olds, 5.1% in those age 55-59, and 6.9% at age 60 or more. Clinically significant serrated polyps followed a similar pattern, with rates of 3.0% before age 40, 5.1% in 40- to 44-year-olds, 6.6% in 55- to 59-year-olds, and 6.0% in those who were older.
In a multivariate logistic regression analysis adjusted for sex, body mass index, smoking, and other potential confounders, 45- to 49-year-olds were at a 243% increased risk of finding advanced adenomas on colonoscopy, compared with those less than 40 years old, while the 50- to 54-year-olds had a virtually identical 244% increased risk.
Dr. Butterly noted that there are now 15,000 cases of colorectal cancer occurring annually in individuals under age 50 in the United States, with 3,600 deaths.
“Prevention of colorectal cancer in young, productive individuals is an essential clinical imperative that must be addressed,” she concluded.
She reported having no financial conflicts regarding her study.