Colonoscopies for patients aged 45–49 years yield positive results

In response to the increase in colon cancer rates in younger individuals in 2018, the ACS—with other organizations following suit—recommended lowering the age for starting colorectal cancer screening of average-risk individuals to 45 years. Researchers from the Stanford University School of Medicine in California believe that enough time has now passed to begin assessing the impact of this change. Specifically, they wanted to examine any changes in the proportion of younger people screened in Stanford endoscopy clinics and whether the inclusion of the younger subjects would dilute the ADR. The study appears in Clinical Gastroenterology and Hepatology (doi:10.1016/j.cgh.2022.04.037.)

The researchers used data from Stanford’s Colonoscopy Quality Assurance Program, which collects information from four of the university’s Northern California endoscopy clinics. The researchers compared subjects who underwent screening colonoscopy during two periods. Period 1 covers October 2017 through December 2018 and represents the time before the 2018 ACS guideline. Period 2 covers January 2019 through August 2021, after dissemination of the new guideline. Subjects from each time period were divided into several groups: patients between the ages of 45 and 49 years and those 50 years old or older (in five-year age groups) at their initial colonoscopies as well as patients in the same age groups who were undergoing rescreening colonoscopy.

For each group and by time period, the researchers compared detection rates for adenomas, advanced adenomas, sessile serrated lesions (SSLs), and advanced SSLs; the mean number of adenomas per colonoscopy; and the mean number of lesions per colonoscopy.

Dr Ladabaum, who is the lead author of the study, and his colleagues compared detection rates from Period 2 to Period 1 for patients aged 45–50 years to explore whether patients at low risk for colorectal neoplasia might be self-selecting for screening in Period 2. “When the ACS guidelines were first published, concerns were raised that the 45- to 49-yearolds who would present for screening might be health-conscious persons with the best access to medical services, and that these persons might in fact be a low-risk group.”

The researchers also compared Period 2 detection rates among the younger patients with those of the older groups (those who underwent initial screening or rescreening) for whom colorectal cancer screening is encouraged under new and previous guidelines.

From records of 29,166 unique colonoscopies, the study selected patients who had undergone colonoscopy with documentation of the extent of examination to the cecum and a Boston Bowel Preparation Score of at least 2 in each segment (indicating bowel preparation that was adequate for visualizing the bowel lining). The final study data set included 7990 patients who had undergone colonoscopies from October 2017 through August 2021; 4266 were first-time colonoscopies, and 3724 were rescreening colonoscopies. The median age of the patients was 56–58 years, and approximately 53% were female.

The researchers found that the proportion of first-time screening colonoscopies performed in patients aged 45–49 years increased from 41 of 1183 during Period 1 to 350 of 3005 during Period 2 (3.5% and 11.6%, respectively; i.e., a 3-fold increase.) They also found that for Period 1, 55.2% of first-time screening colonoscopies were performed on patients between the ages of 50 and 54 years, and 53.9% were performed for the same age group during Period 2. These numbers indicate that the vast majority of initial screenings are being performed in the first five years after the patients become eligible on the basis of the previous screening starting age of 50 years.

They also discovered that rescreening colonoscopies were shifted to older age groups with a bell-shaped distribution around the 60- to 64-year-old group, which probably reflects second screenings among those who had their first colonoscopy in their early 50s. This accounted for the largest proportion of rescreening colonoscopies in both periods (24.8% for Period 1 and 26.1% for Period 2).

Lesion detection rates in the 45- to 49-year category versus the 50- to 54-year category increased to a similar extent from Period 1 to Period 2. The study authors attribute this finding to quality improvement programs at their clinics.

“Our results suggest that screening at ages 45 to 49 is likely to yield substantial long-term benefits, lending support to the recent change in guidelines,” says Dr Ladabaum. “We also believe that 45- to 49-year-olds should be included when calculating ADR.”

Dr Ladabaum also says that this study addresses some of the central concerns regarding the updated screening policy: Will endoscopy units be overwhelmed? Will the yield be low when patients aged 45–49 years are screened, especially if lowrisk people self-select for screening? Should the calculation of the ADR— the key colonoscopy quality metric— include these patients?

“So far, the screening volume in 45- to 49-year-olds has increased only modestly in our unit, and it is still far lower than at ages 50 to 54,” he adds. “Importantly, the detection rates for all, and, crucially, also for advanced precancerous lesions, were only slightly lower at age 45 to 49 years versus age 50 to 54 years, and they were comparable to the yield at repeat screening at ages 60 to 64 years. We think 45- to 49-yearolds should absolutely be included when calculating the ADR.”

Dr Ladabaum notes that it remains to be seen if endoscopic resources will be strained. “We must ensure that screening older, currently unscreened persons is not neglected, and that we ensure access to prompt colonoscopies for all persons with an abnormal noninvasive colorectal cancer screening test, such as an abnormal fecal immunochemical test.”

Rebecca Siegel, MPH, senior scientific director of surveillance research at the ACS in Kennesaw, Georgia, who was not involved with the study, says that the research is important because there were very little data on colorectal cancer screening in average-risk people aged 45–49 years, and many clinicians and researchers were skeptical about screening people younger than 50 years.

“Beforehand,” she says, “the belief was that the risk was too low in people 45 to 49 years old and that there wasn’t evidence that screening would be effective for that population. This study is a vindication for the ACS, which received substantial criticism when it was the first to lower the screening age, and verification for the US Preventive Services Taskforce, which issued a similar guideline last year.”

“Screening has resulted in steep declines in colorectal cancer incidence and mortality in people 50 and older, and now we know the net should be cast wider to include younger people who are now at increasingly higher risk for cancer,” she continues. “This study is facility based and limited geographically, so future research is needed to confirm these findings in a population-based cohort.” The Stanford researchers agree with this limitation, and they also note that they were unable to capture demographic information beyond sex and age.

Siegel says that guidance about colorectal cancer screening, as well as justification for the lower age, can be found on the ACS website (https://www.cancer.org/cancer/colon-rectalcancer/detection-diagnosis-staging/acs-recommendations.html), in the ACS guideline (https://acsjournals.onlinelibrary.wiley.com/doi/full/10.3322/caac.21457), and on the US Preventive Services Task Force website (https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening), where the modeling study and evidence summary can be accessed.