New Roadmap for CRC Screening: Use More Stool Tests, Says AGA

Kristin Jenkins

August 06, 2020

A radical change in screening for colorectal cancer is being proposed in the United States, where the default screening modality to date has been colonoscopy.

Instead, the American Gastroenterological Association (AGA) is proposing new approaches that combine better risk assessment, more use of noninvasive testing (such as fecal occult blood tests), and more targeted referrals for colonoscopy. Such changes could increase patient compliance and "save countless lives," it says.

"We need to improve our strategies to curb the cancer that ranks second for deaths in the US," commented Srinadh Komanduri, MD, chair of the AGA Center for GI Innovation and Technology, in a statement.

"Approximately 67% of eligible Americans are screened for colorectal cancer," he said, which means that a third (33%) are not.

During the COVID-19 pandemic, the proportion of individuals not being screened has increased. One report of medical claims data showed that colonoscopies dropped by 90% during April.

The proposed changes are outlined in an AGA white paper, "Roadmap for the Future of Colorectal Cancer Screening in the United States."

The report, written following consultation with 60 gastroenterology and research experts, was published online in Clinical Gastroenterology and Hepatology.

It proposes that alternative testing modalities to colonoscopy will need to be integrated into organized screening programs.

Instead of offering colonoscopy as the default screening method for all patients at risk, the AGA is advising that it be offered initially only to patients at high risk, which would increase access for those who need it most.

For patients at lower risk, noninvasive screening methods, such as fecal occult blood testing, could be offered initially and then integrated with colonoscopy.

"If we offered tests that were convenient, accurate, and of lower cost, and we could help people choose the best option based on their individual cancer risks, we would save more lives," Joshua E. Melson, MD, MPH, lead author of the AGA white paper and assistant professor at Rush University Medical Center in Chicago, Illinois, told Medscape Medical News.

Screening can reduce CRC mortality by more than 50%, he added.

"Screening should be thought of as a process over time, not a single test isolated in time," Melson commented. A clinical practice that has historically used only colonoscopy will need an organized, structured program to incorporate noninvasive testing, he said.

Revamping of CRC Screening Infrastructure

To date, efforts to increase CRC screening uptake have met with limited success, the AGA says. In 2014, the National Colorectal Cancer Round Table set the bar high with a 2018 screening goal of 80% for adults 50 years of age and older. As of 2020, some states had almost reached this goal, but most had not.

"In the opportunistic screening environment in the US, where colonoscopy is the most prevalent method, CRC screening has not reached aspirational goals in terms of uptake, reduction in CRC incidence, and disease burden," the AGA said. "It is questionable if 80% uptake is achievable in a primarily opportunistic screening environment."

In the proposed revamping of the current CRC screening infrastructure, patients whose physicians recommend CRC screening would no longer be left to their own devices to follow up. Clinicians would initiate CRC screening and oversee follow-up testing at defined intervals and would employ ongoing surveillance.

Ensuring that appropriate screening is readily available to at-risk individuals with no social, racial, or economic disparities is crucial, the AGA says. Racial disparities in access to screening disproportionately burden Blacks and Latinx as well as people living in rural areas. Screening differences account for 42% of the disparity in CRC incidence between Black and White Americans and 19% of the disparity in CRC mortality.

Compared to colonoscopy, which requires bowel preparation, time off from work, and a hospital or clinic procedure, the fecal immunochemical test (FIT), for which a patient provides stool samples that are examined for the presence of blood, is much less stressful: it is noninvasive, and the patients collect the samples themselves in their own home. Studies show that in diverse environments, patients prefer FIT over colonoscopy.

In a controlled trial that involved more than 55,000 patients who were randomly assigned to undergo either FIT or colonoscopy, the participation rate in the first cycle was greater for FIT than for colonoscopy (34.2% vs 24.6%). This partially offset the lower single-application sensitivity for CRC of FIT, the researchers said.

Results from a study with a cluster randomized design showed that offering up-front stool testing as an option in addition to colonoscopy increased screening uptake. Of patients offered fecal occult blood testing or colonoscopy, 69% completed the noninvasive screening, compared with 38% of those offered colonoscopy alone. Notably, non-White participants were more adherent to stool testing.

The success of the AGA's new initiative hinges largely upon the development of affordable, highly accurate, easy-to-use, noninvasive tests. In this regard, the organization has challenged scientists and industry partners with an aspirational target that is "far superior to current methodologies in terms of sensitivity and specificity," said Melson, who is associate professor at Rush Medical College in Chicago, Illinois, and a member of the AGA Center for GI Innovation and Technology.

The AGA wants new CRC screening tests that are capable of detecting advanced adenomas and advanced serrated lesions with a one-time sensitivity and specificity of 90% or higher, which is comparable to colonoscopy.

The FIT test has a sensitivity of less than 50% for detecting an advanced polyp of 10 mm or larger, said Melson.

The multitarget stool DNA (MT-sDNA) test may offer some improvement.

In a 2014 pivotal trial that compared FIT with the MT-sDNA in patients at average risk, the MT-sDNA test had higher sensitivity for detecting nonadvanced CRC lesions than FIT (92% vs 74%) but less specificity (87% vs 95%). The rate of detection of polyps with high-grade dysplasia was 69.2% with DNA testing and 46.2% with FIT.

However, the MT-sDNA test costs more than $500, compared to $25 for the FIT test, Melson pointed out.

To help identify the most appropriate screening for individual patients, better understanding and more thorough identification of risk factors are needed. "Risk assessment is definitely not where it could be," Melson said.

The accuracy of risk assessment can be improved by sharing information from electronic health records on past colonoscopy polyp data, the presence of molecular markers, and family history, the AGA says. "With clearer risk assessment, shared decision-making on the most appropriate test becomes more clear and screening rates would benefit from patient buy-in and from easier access."

The AGA recommends that research focus on the cost-effectiveness of screening younger patients, because the proportion of CRC cases in adults younger than 50 has doubled since 1990.

This has raised the question as to whether the age for initial CRC screening should be lowered to 45 years (it already has been by the American Cancer Society), but there is much debate over this move.

Melson has received consulting fees from Clinical Genomics and research support from Boston Scientific Corporation and holds stocks in Virgo Imaging. A number of AGA white paper coauthors have disclosed relevant financial relationships.

Clin Gastroenterol Hepatol. Published online July 15, 2020. Full text

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