Explore the FDA-approved Guardant Health Shield blood test for colorectal cancer screening. Learn about its advantages, limitations, and what patients need to know before opting for this non-invasive alternative to traditional screening methods.
Colorectal cancer (CRC) remains one of the leading causes of cancer-related deaths globally. Early detection is crucial for improving survival rates, but traditional screening methods like colonoscopy and fecal immunochemical tests (FIT) are often met with resistance due to their invasive nature. The recent FDA approval of Guardant Health’s Shield blood test offers a new, less invasive option for CRC screening, especially for patients at average risk. However, it’s important to weigh the benefits against the risks before adopting this new screening method.
FDA Approval of Guardant Health’s Shield Test:
On July 29, 2024, the FDA approved the Guardant Health Shield blood test, marking the first time a blood test has been authorized as a primary method for CRC screening. This approval provides an alternative to traditional methods, with the test now covered by Medicare, making it more accessible to a broader population. The Shield test is especially significant in addressing the low screening rates in the U.S., which currently stand at 59% due to the invasiveness or unpleasantness of existing methods.
Advantages of the Shield Blood Test:
The Shield blood test offers several advantages, particularly for those who avoid traditional screening methods. The test detects circulating free DNA associated with colon cancers, with high specificity in detecting stages II, III, and IV tumors. This non-invasive test can be easily included in routine blood work, significantly improving screening rates. Early results have shown a 90% completion rate, indicating that more patients are likely to undergo screening when prescribed this test.
Challenges and Risks Associated with the Blood Test:
Despite its benefits, the Shield blood test has limitations that must be communicated to patients. The test is less effective in detecting stage I cancer and precursor lesions, with only 13% of lesions detected in clinical trials. This limitation raises concerns about the test’s ability to prevent cancer by detecting and removing precursor lesions early.
Additionally, the Shield test has a notable rate of false positives. In clinical trials, 10.4% of patients without advanced colorectal neoplasia were incorrectly identified as having a positive test result. This can lead to unnecessary anxiety and further invasive testing, such as colonoscopy, to confirm the results. Cost is another factor, as the price of the Shield test compared to other methods like Cologuard and colonoscopy is still uncertain, potentially making it less cost-effective if not adequately covered by insurance.
Future Implications of the Shield Blood Test:
The introduction of the Shield blood test is a significant development in CRC screening, offering a more appealing option for patients who resist traditional methods. Increasing CRC screening rates is crucial, and a non-invasive test like Shield could encourage more people to get screened. However, it’s essential to ensure that patients understand the limitations of the test and the importance of follow-up procedures, especially in the case of abnormal results.
Healthcare providers should also be aware of potential equity issues, as the Shield test requires a blood draw at a medical facility, which may be inaccessible for some patients, particularly in rural areas. The test’s role in the future of CRC screening will depend on its acceptance by both patients and healthcare providers, as well as its cost and insurance coverage.
Conclusion:
The Guardant Health Shield blood test represents a promising addition to the CRC screening toolkit. Its ease of use and non-invasive nature make it an attractive option for patients at average risk of CRC. However, healthcare providers must thoroughly discuss the benefits and risks with patients, emphasizing the test’s limitations and the need for follow-up care. As CRC becomes more prevalent in younger populations, increasing awareness and screening rates will be critical in reducing the incidence and mortality of this preventable disease.
References:
- The Benefits and Risks of Using Liquid Biopsy for CRC Screening by Julia Bonavitacola on AJMC
- Bonavitacola J. Blood test approved by FDA for screening for colorectal cancer. July 29, 2024. Accessed August 7, 2024. https://www.ajmc.com/view/blood-test-approved-by-fda-for-screening-for-colorectal-cancer
- Guardant Health’s FDA-approved Shield Blood Test now commercially available in U.S. as a primary screening option for colorectal cancer. News release. Guardant Health. August 1, 2024. Accessed August 14, 2024. https://investors.guardanthealth.com/press-releases/press-releases/2024/Guardant-Healths-FDA-approved-Shield-Blood-Test-Now-Commercially-Available-in-U.S.-as-a-Primary-Screening-Option-for-Colorectal-Cancer/default.aspx
- Chung DC, Gray DM II, Singh H, et al. A cell-free DNA blood-based test for colorectal cancer screening. N Engl J Med. 2024;390:973-983. doi:10.1056/NEJMoa2304714
- New data offer reality check on blood-based colorectal cancer screening. News release. American Gastroentrological Association. March 26, 2024. Accessed August 7, 2024. https://gastro.org/press-releases/new-data-offer-reality-check-on-blood-based-colorectal-cancer-screening/
- Guardant Health’s FDA-approved Shield blood test now commercially available in U.S. as a primary screening option for colorectal cancer. News release. Guardant. August 1, 2024. Accessed August 7, 2024. https://investors.guardanthealth.com/press-releases/press-releases/2024/Guardant-Healths-FDA-approved-Shield-Blood-Test-Now-Commercially-Available-in-U.S.-as-a-Primary-Screening-Option-for-Colorectal-Cancer/default.aspx
