Dive Brief:
- A 20,000-subject clinical trial of Exact Sciences’ next-generation colorectal cancer test has met its primary endpoints, positioning the company to file to sell the diagnostic in the U.S. this year.
- Exact Sciences compared data on the new Cologuard test to results from an earlier trial of its existing diagnostic. The analysis suggests the new stool-based test provides more true positives and fewer false positives than its predecessor.
- The new test gives users more time to return samples for analysis than the current one, but it is still potentially less convenient than rival blood-based diagnostics in development.
Dive Insight:
The current version of Cologuard tests for 10 DNA markers, plus blood, in stool samples to show if a patient may have colorectal cancer. People who test positive may then undergo a colonoscopy to show if they have a tumor.
Cologuard competes against the fecal immunochemical test (FIT), which detects blood in stool samples. In the clinical trial of the current version of Cologuard, Exact Sciences’ test was better at detecting cancer than FIT but also gave more false positives. False alarms burden patients and healthcare systems with unnecessary colonoscopies, making specificity a weakness of the existing Cologuard test.
Exact Sciences worked with Mayo Clinic to develop a test with a lower false positive rate. The partners took a different approach with their next-generation test, focusing on methylation markers rather than DNA mutations in an attempt to improve specificity and pre-cancer sensitivity, without reducing cancer sensitivity.
The clinical trial data published Tuesday suggest the attempt succeeded. The next-generation test had a specificity including non-advanced findings of 91%, compared to the 87% reported in the study of the current Cologuard diagnostic.
Overall, the differences between the data on the two tests are small, with advanced precancer sensitivity increasing one percentage point to 43%, but consistently favor the new diagnostic in the limited look at the results released by Exact Sciences. The data are in line with an earlier analysis of the new test.
There are gaps in the top-line data, though. The clinical trial used FIT as a comparator, but Exact Sciences has yet to share data on how that test performed, and the release lacks details such as a breakdown of how Cologuard performed by age and the positive predictive value. The next-generation trial enrolled younger people than the original trial, which showed specificity decreases with age.