Fact checked byHeather Biele

Read more

November 01, 2024
2 min read
Save

False-positive Shield test ‘does not appear’ to correlate with higher non-CRC cancer risk

Fact checked byHeather Biele
You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

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.

Rate of non-colorectal cancer malignancies at 1 year following blood-based Shield test: False-positive result; 0.8% VS True-negative result; 0.9%
Data derived from: 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).

“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.”