False-positive Shield test ‘does not appear’ to correlate with higher non-CRC cancer risk
Key takeaways:
- The rate of non-CRC malignancies at 1 year was 0.8% in the false-positive group and 0.9% in the true-negative group.
- Repeat screening recommendations for false positives should be guided by colonoscopy results.
PHILADELPHIA — Patients with a false-positive Shield test result did not appear to be at increased risk for non-colorectal cancer malignancies at 1 year compared with those with a true-negative result, according to a presenter here.
“Although there are multiple colon cancer screening options available, adherence remains suboptimal and having a blood-based screening modality represents an attractive option that could be completed at any health care encounter,” Daniel C. Chung, MD, medical co-director of the Center for Cancer Risk Assessment and director of the High-Risk GI Cancer Clinic at Massachusetts General Hospital and professor of medicine at Harvard Medical School, said at the ACG Annual Scientific Meeting. “It has been shown that incorporating blood-based testing as a CRC screening option improves overall screening rates.
“False-positive results can occur with any noninvasive screening test, and it is uncertain whether additional follow-up is indicated to evaluate false-positive blood test results after a negative colonoscopy.”
To better understand this, Chung and colleagues reviewed 1-year outcomes of individuals enrolled and tested with Guardant Health’s Shield blood-based, cell-free DNA assay in the prospective, observational, multicenter ECLIPSE study.
The study included 22,877 healthy, average-risk adults aged 45 to 84 years undergoing routine screening with colonoscopy, who provided a blood sample before the procedure and were followed for 2 years for interval malignancies. Of those, 7,861 participants had valid Shield and colonoscopy results and were included in analysis.
According to Chung, the study met its co-primary objectives of CRC sensitivity of 83.1% (95% CI, 72.2-90.3) and advanced neoplasia specificity of 89.6% (95% CI, 88.8-90.3).
Results showed that of 698 patients with a false-positive result, 640 (92%) were available for follow-up and the rate of non-CRC malignancies at 1 year was 0.8% (95% CI, 0.3-1.8).
Similarly, of 5,982 patients with true-negative results, 5,502 (92%) were available for follow-up and the rate of non-CRC malignancies at 1 year was 0.9% (95% CI, 0.7-1.2).
“Our 1-year data indicate that the rate of non-colorectal cancers is not increased in those who had a false-positive Shield result,” Chung told attendees.
No post-colonoscopy CRC was identified at 1 year in the false-positive or true-negative groups, he noted.
“A false-positive Shield test does not appear to correlate with an increased risk for non-colorectal malignancy at 1 year of follow-up,” Chung said. “Our clinical follow-up is ongoing and will continue to gather 2-year cancer diagnoses in enrolled individuals.”
He added, “In individuals with a false-positive Shield test, recommendations for repeat CRC screening should be guided by the colonoscopy findings.”
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Chung DC, et al. Evaluating the risk of non-colorectal cancers in individuals with a false positive blood-based colorectal cancer screening test. Presented at: ACG Annual Scientific Meeting; Oct. 25-30, 2024; Philadelphia (hybrid meeting).
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