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Guidelines that recently lowered the colorectal screening age to 45 for all individuals of average risk were right on track, suggested a retrospective study of predictors for advanced premalignant lesions (APLs) and colorectal cancer.

In a national registry analysis involving over half a million colonoscopies, older age was an independent predictor of risk, reported Steven Itzkowitz, MD, of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues.

For each 1-year increase in age, there was an 8% greater risk of finding advanced colorectal neoplasia by colonoscopy.

However, neoplasia and APL were almost as prevalent among those ages 45 to 49 as in 50- to 54-year-olds, and their rates of colorectal cancer were even higher, the researchers wrote in .

Among adults ages 45 to 49, neoplasia was seen in 32%, APLs in 7.5%, and colorectal cancer in 0.58%. Similar, albeit slightly lower, rates were seen for those ages 40 to 44 (26.6%, 5.8%, and 0.53%, respectively). For those ages 50 to 54, by comparison, neoplasia was seen in 37.7%, APLs in 9.5%, and colorectal cancer in 0.32%.

"The big driver of this study was the need for really good real-world data to inform screening recommendations," Itzkowitz said in a press release. "The data confirm what we have been seeing in the clinic -- that 45 is now the new 50."

The American College of Gastroenterology () first lowered the age to start colorectal screening from 50 to 45 for African Americans in 2009. The expanded that in 2018 to all average-risk individuals, regardless of race or ethnicity, as did the U.S. Preventive Services Task Force in 2020 and the ACG in 2021.

The adjustment in recent guidelines follows a rise in early-onset colorectal cancer among patients younger than 50, whereas rates are declining in older adults.

Early-onset colorectal cancer makes up 12% of all colorectal cancer cases, with cases in those under 45 accounting for 6% of all cases.

"Colorectal cancers arise from precursor lesions: polyps," Itzkowitz said. "But, because polyps are not 'reportable' lesions to national or state health registries, we have little understanding as to how common these precursors are among younger people."

His group examined the GI Quality Improvement Consortium Registry, comprising nearly 3 million colonoscopies from 123 AMSURG ambulatory endoscopy centers, part of Envision Healthcare, across 29 states. Data collection occurred from 2014 to 2021.

Adults up to age 54 who had an initial high-quality colonoscopy, defined by adequate bowel preparation, photographed cecal landmarks, and withdrawal times of over 6 minutes were included. Main outcomes assessed young-onset colorectal cancer (age 18 to 49 years) and neoplasia prevalence and predictors.

Of the 562,559 such colonoscopies first recorded and included for screening or diagnostics, the age breakdown was:

• 94,822 adults up to age 39
• 51,176 ages 40 to 44
• 79,934 ages 45 to 49
• 336,627 ages 50 to 54

Most patients were white (60% to 65%) and more than half were women.

Among adults up to age 44, only a minority of the colonoscopies were for screening; the most common indications were diagnostic, either for bleeding (39%) or "other" (46%).

Common indications for colonoscopies among ages 45 to 49 included 41% for screening and 31% for diagnostic "other."

Among adults ages 50 to 54, nearly all (90%) colonoscopies were done for screening.

Adjusted multivariate logistic regression showed greater risk for APLs and colorectal cancer associated with: being white, increasing age, male (OR 1.67), having a family history of colorectal cancer (OR 1.21) or polyps (OR 1.33), and having a colonoscopy for bleeding (OR 1.15) or screening (OR 1.20; P<0.01 for all).

"Our data also suggest that clinically important lesions occur about 5 years earlier in individuals with a family history of colorectal cancer, compared to those without a family history," Itzkowitz added.

The analysis had several limitations, the researchers acknowledged, including that many records had missing ethnicity data and that the registry data did not include the location of colonic pathological findings.

Also, there was potential bias from use of insurance data and other patient-preferred endoscopic centers. However, results should be generalizable to ambulatory surgical centers, they wrote.

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