FDA approves new blood test to screen for colon cancer
The FDA has approved a new blood test from Guardant Health, called Shield, to screen for colon cancer. This test is not a replacement for colonoscopies, but it has the potential to increase the number of people screened for colorectal cancer, especially among younger adults not yet eligible for routine colonoscopies.
Previously, Shield was available to doctors for $895 out-of-pocket. Now, with FDA approval, Medicare and private insurance are more likely to cover the cost, making the test more accessible.
Dr. Arvind Dasari from the University of Texas MD Anderson Cancer Center called the approval a “welcome development,” but noted the need to observe its impact on screening rates and mortality reduction. The American Cancer Society estimates that over 53,000 people will die of colorectal cancer this year.
Research in March showed Shield is 83% effective in detecting colorectal cancers by identifying DNA released by tumours into the bloodstream. However, it is less effective at detecting early-stage polyps, only identifying 13%.
The test is recommended every three years starting at age 45, the same age for starting colorectal screening.
A positive Shield test does not confirm cancer; a follow-up colonoscopy is necessary to locate and assess tumours. Robert Smith of the American Cancer Society emphasised the importance of confirming positive Shield results with a colonoscopy.
Shield is the second blood test approved for colon cancer screening, following Epigenomics’ Epi proColon in 2016, which is rarely used due to accuracy concerns and lack of insurance coverage.
Colorectal cancer is unique in its preventability through screening, with colonoscopy being the most accurate method. Yet, screening rates are low, with fewer than 60% of eligible individuals screened. Dr. Sapna Syngal from Dana-Farber Cancer Center noted the potential impact of increased screenings through the Shield test.
Adults in their 40s and 50s, often busy with work and family, are the least likely to adhere to screening recommendations. Colonoscopies are time-consuming and require a laxative regimen the day before, which many find unpleasant.
Electra Paskett from Ohio State University Comprehensive Cancer Center highlighted that a blood test might be more appealing to many people compared to the messiness of stool tests and the invasiveness of colonoscopies. Other screening methods include faecal occult blood tests and FIT-DNA tests like Cologuard, which are effective at detecting cancer but less so at identifying precancerous polyps.
John Gormly, 77, from Newport Beach, California, avoided colonoscopy screenings for years but opted for the Shield blood test. When results indicated potential cancer, a follow-up colonoscopy confirmed stage 2 colon cancer, which was successfully removed surgically. Gormly credits the blood test for his timely diagnosis and treatment.
