National CRC Screening Summit

Issaka

Pdf Summary

This presentation by Dr. Rachel Issaka reviews recent advances and challenges in blood-based colorectal cancer (CRC) screening tests, focusing on circulating cell-free DNA (cf-DNA) and circulating tumor DNA (ct-DNA) assays, often referred to as “liquid biopsy.” These tests detect tumor-derived DNA fragments in blood, offering a less invasive screening alternative.<br /><br />Key blood-based tests discussed include Epi proColon (detecting methylated SEPT9 DNA), Guardant Health’s cfDNA Shield (ECLIPSE study), and Freenome’s ctDNA SimpleScreen (PREEMPT CRC study). Both ECLIPSE and PREEMPT enrolled large, diverse cohorts and showed similar CRC sensitivities (~79-83%) and specificities (~89-91%) comparable to stool-based tests. However, sensitivities for advanced precancerous lesions and polyps remain low (about 12-13%), which is inferior to colonoscopy or stool testing. Advanced lesion sensitivity was slightly higher in the PREEMPT study.<br /><br />Significant concerns include suboptimal follow-up colonoscopy completion after positive tests (only about 56%) and potential impacts on health disparities. Blood-based tests risk widening disparities if they displace established tests in underserved populations, are costly, or suffer poor adherence to follow-up procedures. Conversely, with thoughtful policy and implementation prioritizing high-risk groups and accessible cost, they could improve screening uptake and equity.<br /><br />Cost-effectiveness remains limited given current performance metrics. Though blood-based tests have comparable CRC detection to stool tests, their lower sensitivity for precancerous lesions and challenges with follow-up reduce overall benefit in preventing cancer and deaths.<br /><br />In conclusion, while blood-based CRC screening shows promise, especially in enhancing screening participation, challenges remain in improving sensitivity for precancerous lesions, ensuring follow-up colonoscopy, addressing cost, and preventing worsening disparities. Strong cooperation between gastroenterology and primary care is essential for successful integration.<br /><br />Funding for this research came from NIH/NCI and family endowments. Dr. Issaka is affiliated with Fred Hutchinson Cancer Center and University of Washington.

Keywords

colorectal cancer screening

blood-based tests

circulating cell-free DNA

circulating tumor DNA

liquid biopsy

Epi proColon

Guardant Health cfDNA Shield

Freenome ctDNA SimpleScreen

screening sensitivity and specificity

health disparities in cancer screening