These new tests aren’t radical departures from the standard FIT. Like the standard test, the multitarget FIT uses antibodies to test for hemoglobin in stool samples. But these multitarget approaches take the standard FIT a step further by testing for additional DNA, RNA, or protein biomarkers associated with CRC to help improve early detection.
Currently, the US Preventive Services Task Force (USPSTF) recommends two FIT tests — standard FIT and stool FIT-DNA — as well as a third noninvasive CRC screening test, guaiac fecal occult blood test (gFOBT). gFOBT detects heme, a component of hemoglobin, through a chemical reaction.
But both standard FIT and stool FIT-DNA come with caveats. Compared to the standard test, FIT-DNA tends to be better at detecting traces of blood in the stool, and thus can uncover more instances of CRC or other advanced lesions. The flipside is that the DNA test also often leads to more false-positive findings.
In fact, the American College of Physicians does not recommend stool FIT-DNA for screening, citing issues such as cost — more than $600 per test vs about $30 for standard FIT — and the greater likelihood of false-positives compared with both standard FIT and gFOBT.
Given these trade-offs with current noninvasive screening options, developing a FIT option that can improve early detection of CRC and advanced precancerous lesions without increasing false-positives could make a big difference in outcomes.
Three new noninvasive multitarget tests under investigation — an updated DNA-based test, Cologuard 2.0 (Exact Sciences; Madison, WI); an RNA-based test, ColoSense (Geneoscopy; St Louis, MO); and a protein-based test from CRCbioscreen (Amsterdam, the Netherlands) — may be able to do just that.
Cologuard 2.0: Multitarget Stool DNA-Based Test
An updated version of the stool FIT-DNA is currently under development. Dubbed Next Generation Cologuard, or Cologuard 2.0, this multitarget test detects three novel methylated DNA markers along with fecal hemoglobin.
In a recent trial comparing Cologuard 2.0 vs standard FIT, 20,176 participants aged 40 years or older were screened with Cologuard 2.0 as well as standard FIT before they all also received a colonoscopy. The researchers compared findings with Cologuard 2.0 and standard FIT, which used a positivity cutoff ≥ 20 mcg hemoglobin/g feces.
The researchers then assessed Cologuard 2.0’s sensitivity (a gauge of how well it detects disease that is truly present) and specificity (a measure of how well a test indicates the absence of disease when no disease is present) compared with standard FIT and the original Cologuard test.
Overall, Cologuard 2.0 demonstrated better sensitivity for CRC than did standard FIT (93.9% vs 67.3%, respectively) and for advanced precancerous lesions (43.4% vs 23.3%). The next-generation test, for instance, identified 92 of 98 participants with colonoscopy-confirmed CRC diagnoses vs 66 cases using standard FIT.
Compared with the original Cologuard, Cologuard 2.0’s sensitivity improved slightly for CRC, from 92% to 93.9%,; for advanced precancerous lesions, from 42% to 43.4%; and for high-grade dysplasia, from 69% to 75%. Specificity also improved with the latest version, from 87% to 90.6%.
However, Cologuard 2.0’s specificity for advanced neoplasia was worse than that of standard FIT (90.6% vs 94.8%, respectively), which would increase the likelihood of false-positive findings.
Despite its lower specificity compared with standard FIT, Cologuard 2.0 has several advantages. The test can identify more people with CRC and advanced precancerous lesions than the standard test and can lead to fewer false-positives than the original Cologuard test.
Cologuard maker Exact Sciences has submitted trial data to the US Food and Drug Administration (FDA) for approval.