From the AGA Journals

Earlier colorectal cancer screening appears cost-effective in overweight, obese patients

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Is the juice worth the squeeze?

Obesity is associated with an increased risk of colorectal cancer, along with cancers of the breast, endometrium, and esophagus. Even maternal obesity is associated with higher offspring colorectal cancer rates. Key mechanisms that underlie these associations include high insulin levels in obesity that propel tumor growth, adipose tissue that secretes inflammatory cytokines, and high glucose levels that act as fuel for cancer proliferation.

Sarah McGill, MD, MSc, FACG, FASGE, is associate professor medicine, gastroenterology, and hepatology at the University of North Carolina at Chapel Hill.

Dr. Sarah McGill

With the recommended start of colorectal cancer screening now at age 45, and the U.S. demographic obesity problem worsening, Yeoh and his Stanford colleagues put their well-described cost-effectiveness model to work to analyze screening at different body mass indices. The new inputs consider not only higher colorectal cancer risk among obese individuals, but also increased all-cause mortality.

For men with BMI over 35, moving the colonoscopy screening age earlier to age 40 was cost-effective. However, it’s not clear that in practice the juice is worth the squeeze. Changing screening initiation times further based on personalized factors such as BMI could make screening more confusing for patients and physicians and may hurt uptake, a critical factor for the success of any screening program.

The study supports the current paradigm that screening starting at age 45 is cost-effective among men and women at all BMI ranges, a reassuring conclusion. It also serves as a sobering reminder that promoting metabolic health in our patients, our schools, and our communities is a valuable endeavor.

Sarah McGill, MD, MSc, FACG, FASGE, is associate professor medicine, gastroenterology, and hepatology at the University of North Carolina at Chapel Hill. She receives research funding from Olympus America, Finch Therapeutics, Genentech, Guardant Health, and Exact Sciences.



Starting colorectal cancer screening earlier than age 50 appears to be cost-effective for both men and women across all body mass index (BMI) measures, according to a study published in Clinical Gastroenterology and Hepatology.

In particular, colonoscopy is cost-effective at age 45 for all BMI strata and at age 40 in obese men. In addition, fecal immunochemical testing (FIT) is highly cost-effective at ages 40 or 45 for all BMI values, wrote Aaron Yeoh, MD, a gastroenterologist at the Stanford (Calif.) University, and colleagues.

Increased body fatness, defined as a high BMI, has increased sharply in recent decades and has been associated with a higher risk of colorectal cancer (CRC). Given the rising incidence of CRC in younger people, the American Cancer Society and U.S. Preventive Services Task Force now endorse screening at age 45. In previous analyses, Dr. Yeoh and colleagues suggested that the policy is likely to be cost-effective, but they didn’t explore the potential differences by BMI.

“Our results suggest that 45 years of age is a reasonable screening initiation age for women and men with BMI ranging from normal through all classes of obesity,” the authors wrote. “Before changing screening policy, supportive data from clinical studies would be needed. Our approach can be applied to future efforts aiming to risk-stratify CRC screening based on multiple clinical factors or biomarkers.”

The research team examined the potential effectiveness and cost-effectiveness of screening tailored to BMI starting as early as age 40 and ending at age 75 in 10 separate cohorts of men and women of normal weight (18.5 to <25 kg/m2), overweight (25 to <30 kg/m2), and three strata of obesity – obese I (30 to <35 kg/m2), obese II (35 to <40 kg/m2), and obese III (>40 kg/m2).

For each cohort, the researchers estimated incremental costs per quality-adjusted life year (QALY) gained by initiating screening at age 40 versus age 45 versus age 50, or by shortening colonoscopy intervals. They modeled screening colonoscopy every 10 years (Colo10) or every 5 years (Colo5), or annual FIT, offered from ages 40, 45, or 50 through age 75 with 100% adherence, with postpolypectomy surveillance through age 80.

For model inputs, the research team favored high-quality data from meta-analyses or large prospective trials. Screening, treatment, and complication costs were set at 2018 Centers for Medicare & Medicaid Services rates for ages 65 and older and modified to reflect commercial costs at ages 65 and younger. The authors assumed use of moderate sedation, and sensitivity analyses addressed possible increased costs and complications of colonoscopy under propofol.

Overall, without screening, sex-specific total CRC deaths were similar for people with overweight or obesity I-III and slightly higher than for people with normal BMI. For both men and women across all BMI strata, Colo10 or FIT starting at age 50 substantially decreased CRC incidence and mortality versus no screening, and the magnitude of the clinical impact was comparable across BMI.

For both sexes across BMI, Colo10 or FIT starting at age 50 was highly cost-effective. The cost per QALY gained for Colo10 compared with no screening became more favorable as BMI increased from normal to obesity III. FIT was cost-saving compared with no screening for all cohorts and was cost-saving or highly cost-effective compared with Colo10 within each cohort.

Initiating Colo10 at age 45 showed incremental decreases in CRC incidence and mortality, which were modest compared with the gains of Colo10 at age 50 versus no screening. However, the incremental gains were achieved at acceptable incremental costs ranging from $64,500 to $85,900 per QALY gained in women and from $33,400 to $64,200 per QALY gained in men.

Initiating Colo10 at age 40 in women and men in the lowest three BMI strata was associated with high incremental costs per QALY gained. In contrast, Colo10 initiation at age 40 cost $80,400 per QALY gained in men with obesity III and $93,300 per QALY gained in men with obesity II.

FIT starting at ages 40 or 45 yielded progressively greater decreases in CRC incidence and mortality for both men and women across BMI strata, and it was highly cost-effective versus starting at later ages. Compared with Colo10, at every screening initiation age, FIT was cost-saving or preferred based on very high incremental costs per QALY, and FIT required substantially fewer colonoscopies per person.

Intensifying screening by shortening the colonoscopy interval to Colo5 was never preferred over shifting Colo10 to earlier screening initiation ages. In all cohorts, Colo5 was either less effective and more costly than Colo10 at a younger age, or when it was more effective, the cost per QALY gained was substantially higher than $100,000 per QALY gained.

Additional studies are needed to understand obesity-specific colonoscopy risks and costs, the authors wrote. In addition, obesity is only one of several factors that should be considered when tailoring CRC screening to the level of CRC risk, they wrote.

“As the search for a multifactor prediction tool that is ready for clinical application continues, we face the question of how to approach single CRC risk factors such as obesity,” they wrote. “While screening guidelines based on BMI can be envisioned if supportive clinical data accumulate, clinical implementation must overcome operational challenges.”

The study funding was not disclosed. One author reported advisory and consultant roles for several medical companies, and the remaining authors disclosed no conflicts.

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