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Noninvasive Stool Test Effective for Colon Cancer Screening

Fran Lowry
February 26, 2019

Fecal immunochemical tests (FITs), used annually, are effective for screening for colorectal cancer (CRC) in average-risk, asymptomatic adults, according to a new meta-analysis.

"Our results provide the strongest evidence to date to support recommendations that average-risk patients can safely opt for an annual, easy-to-use home stool test instead of a screening colonoscopy," lead author Thomas Imperiale, MD, Lawrence Lumeng Professor in Gastroenterology and Hepatology at Indiana University School of Medicine and the Regenstrief Institute, Indianapolis, told Medscape Medical News.

"I would like to see patients be more aware of the options for colorectal cancer screening, the options to colonoscopy, and to be able to bring it up if their primary care providers don't mention FIT as an option," Imperiale added.

The meta-analysis was published online February 25 in the Annals of Internal Medicine.

The US Preventive Services Task Force currently recommends screening for CRC for persons aged 50 to 75 years using any of several options: fecal occult blood testing (a category that includes FIT), sigmoidoscopy, colonoscopy, and other tests. It does not recommend one screening modality over another.

Colonoscopy is considered to be the "gold standard" for CRC screening in the United States, but only 60% to 65% of the eligible American population is current with screening, the authors note. Several other countries, especially those in which healthcare finances are limited, use annual or biennial stool blood tests or a combination of stool testing and lower endoscopy for screening, they note.

Study Details

For the meta-analysis, Imperiale and coauthors reviewed and analyzed the findings of 31 studies that evaluated FIT sensitivity and specificity for CRC. The review included 120,255 asymptomatic participants and 18 FITs.

FITs used in the studies included OC-Sensor (Eiken Chemical), which was used in 14 (58%) of the studies, OC FIT-CHEK (Eiken Chemical), OC-Light (Eiken Chemical), OC-Hemodia (Eiken Chemical), and FOB Gold (Sentinel Diagnostics).

Performance characteristics of FITs depended on the threshold for a positive result.

A threshold of 10 μg/g resulted in a sensitivity of 0.91 (95% confidence interval [CI], 0.84 – 0.95) and a negative likelihood ratio of 0.10 (CI, 0.06 – 0.19) for CRC, whereas a threshold of >20 μg/g resulted in specificity of 0.95 (CI, 0.94 – 0.96) and a positive likelihood ratio of 15.49 (CI, 9.82 – 22.39).

The researchers also evaluated performance characteristics of FITs for advanced adenomas in average-risk individuals who underwent screening colonoscopy.

There, FITs were much less sensitive for advanced adenomas. Sensitivity was 0.40 (CI, 0.33 – 0.47), and the negative likelihood ratio was 0.67 (CI, 0.57 – 0.78) at 10 μg/g. At >20 μg/g, the specificity was 0.95 (CI, 0.94 – 0.96), and the positive likelihood ratio was 5.86 (CI, 3.77 – 8.97).

Not All FITs Are Created Equal

"Our results suggest a need for a head-to-head comparison of different FITs at various thresholds for both colorectal cancer and advanced adenomas," Imperiale said.

In an accompanying editorial, James Allison, MD, University of California, San Francisco, and emeritus investigator in Kaiser Permanente's Division of Research, writes that the systematic review "may help to reassure physicians and patients about the performance of FITs for CRC detection."

In an interview with Medscape Medical News, Allison noted that some primary care physicians in the United States, as well as many of their patients, may be unaware that FITs are similar in effectiveness to colonoscopy when used in a consistent, programmatic way to screen for CRC.

"We've got to get away from the idea that there's only one good test for colon cancer screening. We must increase our national screening for CRC numbers, especially in the vulnerable population — the uninsured, underinsured, poor. Calling a colonoscopy screening test the best, or the gold standard, is not helpful or true. It's a good test, and I'm not saying don't have a colonoscopy. I'm saying don't limit yourself to colonoscopy because it's called the best or gold standard by some," he said.

"There is not one US colorectal cancer screening guideline as of 2019 that says that colonoscopy is the best, gold-standard test. FIT is right up there with colonoscopy," Allison added.

He also cautioned that average-risk individuals who undergo screening with FIT must be sure that the FIT supplied by their physician or healthcare system has been carefully studied and that its advertised performance characteristics have been confirmed.

"The FDA's approval of FITs as simple tests for blood rather than for advanced colorectal neoplasms has allowed for clearance of low-performing tests. There are 120 FDA-cleared FITs on the market. Several of them are produced in foreign countries, China in particular. Many of them are marketed as being as good as the tests that have been well tested, and they are not," he warned.

Addressing physicians, he said, "To make sure you are ordering the best FIT for your patient, go to the latest US Preventive Services Task Force guidelines of 2017."

Allison called for changes to existing laws that charge copays for a colonoscopy performed after a patient receives a positive result on FIT.

"We need better and more consistent payment policies that ensure coverage of colonoscopy after an abnormal FIT test," he said.

The study was funded by the Department of Medicine of Indiana University School of Medicine. Imperiale and Allison report no relevant financial relationships.

Reviewed on 2/27/2019

SOURCE: Medscape, February 26, 2019. Ann Intern Med. Published online February 25, 2019.

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