FDA approves first blood test for colorectal cancer

This week, the U.S. FDA approved the first use of a liquid biopsy (blood test) for colorectal cancer screening. The test, called Shield, is expected to launch commercially within the next week and is the first blood test to be approved by the FDA as a primary screening option for CRC that meets requirements for Medicare reimbursement.

While the convenience of a blood test could potentially encourage more people to get screened, expert consensus is that blood tests can't prevent CRC and should not be considered a replacement for a colonoscopy. Modeling studies and expert consensus published earlier this year in Gastroenterology and Clinical Gastroenterology and Hepatology shed light on the perils of liquid biopsy.

"Based on their current characteristics, blood tests should not be recommended to replace established colorectal cancer screening tests, since blood tests are neither as effective or cost-effective, and would worsen outcomes," said David Lieberman, MD, chair, AGA CRC Workshop chair and lead author of an expert commentary on liquid biopsy for CRC screening.

5 key takeaways

1. A blood test for CRC that meets minimal CMS criteria for sensitivity and performed every three years would likely result in better outcomes than no screening.
2. A blood test for CRC offers a simple process that could encourage more people to participate in screening. Patients who may have declined colonoscopy should understand the need for a colonoscopy if findings are abnormal.  
3. Because blood tests for CRC are predicted to be less effective and more costly than currently established screening programs, they cannot be recommended to replace established effective screening methods.
4. Although blood tests would improve outcomes in currently unscreened people, substituting blood tests for a currently effective test would worsen patient outcomes and increase cost.
5. Potential benchmarks that industry might use to assess an effective blood test for CRC going forward would be sensitivity for stage I-III CRC of >90%, with sensitivity for advanced adenomas of > 40-50%.

"Unless we have the expectation of high sensitivity and specificity, blood-based colorectal cancer tests could lead to false positive and false negative results, which are both bad for patient outcomes,"