FDA approves new colorectal cancer screening test

September 4, 204

Expected results of new colorectal cancer screening test

Each block represents one of 10,000 people between ages 45 and 65

The FDA approved a new blood test for colon cancer screening (Shield from Guardant) in late July. The test detects cell-free DNA from colorectal cancers (CRC) and has been approved for use in those ages 45 and older. This new test has been covered widely in the media (1) (2) (3), and I’ve heard from a number of companies wondering whether and how to cover this test.

The New England Journal published results of a validation study with over 7,800 participants with stage I – III colorectal cancer and found that the test has an 83% sensitivity (meaning that 83 out of 100 with colorectal cancer will be positive on the test) and a 90% specificity (meaning that 90 out of 100 who do not have colorectal cancer will have a negative test). The test has only a 13% sensitivity in detecting colonic polyps that are precursors to cancer.

The graphic above demonstrates what this means in a population with 10,000 members between ages 45-65. We’d expect about six new cases of colon cancer in this population, depicted in red and blue. (I’ve calculated this using American Cancer Society CRC incidence rates with Department of Labor workforce age distribution data.) With an 83% sensitivity, we’d expect to find five out of six true cases of new CRC. With a 90% specificity, we would expect to see 1,000 false positives out of the 10,000 members. This means that negative tests are highly accurate (only one case of cancer among 9,000 negative test results). However, 99.5% of the positive tests (1,000 out of 1,005) will be false positives.

The cost of this test is $895. If all 10,000 members were evaluated with this test, the cost would be about $9 million, or $1.8 million per cancer found. This represents just the cost of this blood test, not the cost of colonoscopies or other CRC tests.

Implications for employers:

• This test is approved by the FDA, but there is not yet data to determine whether the test leads to decreased premature death or better quality of life. Colonoscopies and FIT test screening have each already been demonstrated to decrease deaths from colorectal cancer.

• This test has not yet been evaluated by the US Preventive Services Task Force (USPSTF), and it’s not clear how it would fit into current screening recommendations. FIT tests for colonoscopies could detect worrisome precancerous lesions earlier.

• Employers should review the technology assessment findings of their carriers when these are available, and not rush to provide coverage for this newly approved test.

  
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