Multitarget Stool RNA-Based Test
ColoSense, an RNA-based stool test, looks for eight RNA biomarkers associated with CRC.
The company says that RNA-based testing has an advantage over DNA biomarker assays, such as the currently marketed Cologuard test, because it isn›t subject to the age-related changes in DNA methylation that can throw off the results from DNA assays.
Like Cologuard 2.0, Geneoscopy’s Colosense test is under review by the FDA.
The data Geneoscopy submitted to the FDA came from the CRC-PREVENT trial, which included 8920 participants who were screened with both ColoSense and standard FIT before all had a colonoscopy. The participants ranged in age from 45 to 90 years, with 22% between 45 and 50 years old, a population recently added to the USPSTF screening recommendations.
ColoSense showed higher sensitivity than standard FIT for the presence of CRC (94% vs 78%, respectively) and advanced adenomas (46% vs 29%). In the group aged 45-50 years, the RNA-based test had a sensitivity of 100% for CRC, correctly identifying all five people with colonoscopy-confirmed CRC, and 45% for advanced adenomas.
However, ColoSense was less specific than standard FIT compared with negative colonoscopy findings (88% vs 96%, respectively) and negative findings for advanced lesions or CRC (85.5% vs 94.9%); thus, it was more likely to lead to false-positive results.
Overall, the investigators said ColoSense is comparable to Cologuard — its chief market rival — in terms of sensitivity for CRC and advanced adenomas but has higher sensitivity for colorectal neoplasia in people aged 50 years or younger.
Multitarget Protein-Based Test
The multitarget protein-based FIT uses antibodies to test for two additional proteins: calprotectin, an inflammatory marker associated with CRC, and serpin family F member 2, a protease inhibitor thought to be upregulated in colon cancer.
A 2021 study of 1284 patients found that the sensitivity of the multitarget protein-based test was 42.9% for advanced neoplasias compared with 37.3% with standard FIT. Its specificity was similar to that of standard FIT, at 96.6% for advanced neoplasias.
In a more recent report published in The Lancet Oncology, the team modeled three scenarios comparing the two FIT tests. These scenarios used different cutoff values for a test to be positive for CRC or an advanced lesion.
Overall, the analysis included stool samples from 13,187 patients aged 55-75 years who were in the Netherlands’ national CRC screening program. Stool samples were evaluated with both the multitarget test and the standard FIT, using a positivity cutoff ≥ 47 mcg hemoglobin/g feces. Colonoscopy data were available for only 1270 participants.
In scenario 1, the multitarget test had a lower threshold for a positive test and consequently identified more precancerous lesions than the standard FIT (828 vs 354, respectively). The multitarget FIT identified a few more CRC cases: Of 29 colonoscopy-confirmed CRC cases, the multitarget FIT identified 26 vs 23 with standard FIT.
But the multitarget FIT also had more than double the number of false-positives than the standard FIT (347 vs 161, respectively).
Perhaps the most telling comparison occurred in scenario 2, with both tests set at the same low positivity threshold to minimize false-positives.
As expected, the two tests had similar positivity rates for advanced lesions, with the multitarget test correctly identifying 22 of 29 people with CRC, one fewer than the standard test. The protein-based test identified slightly more people with advanced lesions (156 vs 136 with the standard test), leading to a higher sensitivity for advanced lesions.
Most notably, the protein-based test resulted in fewer false-positives than did the standard test (295 vs 311, respectively) , resulting in a slightly higher specificity.
In this scenario, “a single screening round might not have the biggest impact on cancer incidence and mortality,” the authors said, but the higher detection rate would still accumulate over 20 years of testing. The authors estimated that, under this scenario, substituting the multitarget FIT for the standard test in the Netherlands’ CRC screening program could reduce CRC incidence by 5% and CRC mortality by 4%.
Gerrit Meijer, MD, PhD, a pathologist at the Netherlands Cancer Institute, and colleagues recently launched a company called CRCbioscreen to commercialize this multitarget FIT for large-scale programs. The company›s priority is to develop and validate a clinical-grade test to sell to federal governments with national screening programs, such as those throughout Europe, Australia, and Asia, Dr. Meijer told this news organization. Dr. Meijer expects this process will take about 4 years.
The test will be developed for the US market, but with no nationwide screening program in the United States, future availability will depend on interest from providers and institutions, noted Dr. Meijer, who is also chief scientific officer at CRCbioscreen.
Overall, these three new multitarget stool-based CRC screening tests could help catch more cancers and advanced precancerous lesions. And, if the tests have a high enough specificity, a negative test result could also allow people to forgo screening colonoscopy.
Still, people with a positive FIT finding would require follow-up colonoscopy, but about 10% of patients decline colonoscopy following an abnormal FIT, Mark A. Lewis, MD, director of gastrointestinal oncology at Intermountain Health in Murray, Utah, told this news organization last year. That means that even if precancerous lesions and CRC are being caught earlier, treatment can’t be started unless people follow through with colonoscopy.
A version of this article appeared on Medscape.com.